The MGA With An Attitude
ENGINE OIL General Tech - OF-104
Everything you probably didn't need to know about engine oil.

At 09:45 PM 9/10/04 -0400, Raymond Poulin wrote:
>"I read countless pros & cons of different types of oil. I feel you do the most driving of an MGA with a good common sense attitude. What is your preference when it comes to oil?"

The short answer is, my personal preference is 10W40 all year round, and it doesn't matter which brand. You can ignore all the hype and commercials and everyone's loudly broadcast opinions, close your eyes and plug your ears, and grab whatever is on the first shelf you come to. You can stop here and hit the Delete button, and you don't need to read the rest of the message.

Still here? Then you get the long answer (really long answer), along with a little education, because you're not the first to ask.

I do not like non-detergent oil in an engine, because it allows gunk to settle out in the sump and allows things inside to be coated with dirt and carbon over long periods of time. Detergent oil keeps an engine MUCH cleaner inside, and keeps gunk in suspension until it can get filtered out in the oil filter. These days I believe non-detergent is only available in single weight grades (commonly used in stationary gearbox applications), or in specialty oil for 2-stroke engine fuel mix (where you don't want the additives to gum things up in the combustion chamber).

Non-detergent oil may also be used for hydraulic oil, for shock absorbers, and for some gear oil, as those applications commonly have no oil filter and would just as well see sludge settle out as remain in suspension in the oil. But even then they are likely to be multi-weight specification, and may also contain anti-foaming agents. Hydraulic jack oil is cheap and good for use in Armstrong shock absorbers. I also have another article about gearbox oil.

I do NOT like single weight oil in an engine, like 30 weight or 30W-30, because it changes viscosity too much (thins out when it gets hot, or gets too thick in very cold weather).

In case you didn't know, the "W" in the grade designation stands for "Winter". The very earliest "multi-weight" motor oil was 30W-30, soon followed by 20W-20, 10W-10 and finally 40W-40. These were available in the early 1960's. They were the first oils to contain viscosity index modifiers to prevent them from changing viscosity too much with large temperature changes. Prior to that we had to make seasonal oil changes to run 20 or 10 weight in very cold weather so the car would start, but change back to 30 weight for warm weather so the bearings wouldn't fail. (That was that same era when we used to use alcohol in the cooling system in winter to prevent freezing, and change to water in the summer to prevent boiling). 30W-30 oil is actually lower viscosity than 30 weight when cold, but it doesn't thin out so much when it gets hot. So 30W-30 will be about the same viscosity as 30 weight when hot, but will be easier to start your engine in Winter. That's the origin of the "W" designation. It is an easy starting Winter oil that protects the engine as well as 30 weight.

Oil originally specified for the MGA was 30 weight non-detergent, but only because that was what was traditionally available at the time the cars were built. When straight 30 weight oil gets hot it gets very thin and runs like water. In sub-freezing temperatures it gets quite thick, and the engine might be hard to crank for starting. If you have never seen straight 30 weight oil, it looks and pours like 20W-50 at room temperature, gets MUCH thicker at very cold temperatures, and thin almost like water in a hot running engine in mid summer. At -20dF you can scoop up straight 30 weight oil with a putty knife (almost like wheel bearing grease). So it was common in those days to switch to 20 or even 10 weight oil for very cold weather, then switch back to 30 weight for warmer weather. Such seasonal oil changes can be a PITA, especially if you don't drive much.

In the 1950's it was fairly common for race cars to use Casterol in the engines. In those days this stuff was not made from crude oil, but was peanut oil (I think), or maybe squeezed from the Castor bean as the name implies. It was considerably more expensive than contemporary motor oil, but was used for racing engines because it held the viscosity much better at high temperature. It was a memorable experience to smell the Casterol at the race track. You could almost lick your lips and enjoy the stuff from track side.

The first true multi-season oil was 20W-30, very soon followed by 10W-30, which was commonly available by the mid 1960's. These have more of the viscosity index modifier additives, so they change viscosity less with wider temperature range. Functionally, 10W-30 protects the engine as well as straight 30 weight, and allows it to crank over as easy as straight 10 weight in cold weather. It still gets somewhat thinner when it gets hot, just not nearly as much change in viscosity. 10W-30 was the first real multi-season motor oil that you could run all year round without seasonal oil changes in cold climates (like in Chicago).

The 1960's was a transitional period for engine oil, and for people's perception of engine oil, and for dealing with long standing suspicions (and cost) of the new products. In the late 60's the shelves at the corner service station held non-detergent straight weight oil, 20 and 30 weight in summer, 10 and 20 weight in winter. The shelves also held 20W-20, 30W-30, and 10W-30 oil, as well as at least one major brand and the cheaper house brand. What you put in the customer's car was whatever the customer wanted, and you didn't waste a lot of time trying to argue through a religious war. Today the brake fluid religious wars are running into the same kind of discussions with silicone vs others (for at least two decades).

By the late 1960's you could get 10W40 oil, if you looked around enough. I bought a 1969 Austin America new in late 1969. It had an automatic transmission, and like the front wheel drive Morris Mini and MG 1100 before it, the gearbox was under the engine and ran in engine oil. It needed 10W-40 oil all year round (and 3000 mile oil changes to boot). At that time this oil cost $1.60/qt through the new car dealer, while 10W-30 was about $.36/qt at a corner gas station. Re-refined 30 weight which I used in my MGA in the late 60's was never higher than $.25/qt). ! was so happy when I found Valvoline 10W-40 oil for $1.10/qt at a LARGE auto parts store.

Within a couple of years I was also absolutely elated to discover how clean an engine might be inside after some years of using detergent oil, how little gunk would ever be found in the sump, and how little sludge would accumulate in the oil filter. It was nice to be able to ditch the felt oil filters and use cheaper paper oil filters, and extend oil change intervals from 2000-3000 miles up to 3000-6000 miles.

By the mid 70's you could get 20W-50 oil, which was actually specified for the MGB engine during late production (but not for very cold weather). A problem with 20W-50 is that it gets thick enough at sub-freezing temperatures (maybe even at 40dF) to cause flow problems and show low oil pressure for the first few minutes after starting in cold weather. You can use it in winter, as long as your engine will actually crank and start, but take it easy driving until it warms up and shows normal oil pressure.

Then we started to get synthetic oils. You will find the word "synthetic" many times to follow. Note that synthetic oil is NOT a witch's brew of odd chemicals or solvents. It is still composed primarily of crude oil base stock. The significant feature of synthetic oil is that it has been polymerized, chemically altered to combine small molecules into larger long chain molecules. These larger molecules tend to line up in more orderly fashion between working mechanical surfaces to provide a slightly tougher protective layer with a little less friction.

Synthetic oils were at least four times as expensive as regular oil, and in general synthetic oil still is more expensive. Today you can get synthetic oil in virtually any viscosity specification, including 10W-50, 5W-50, and 0W-50. Yup. The 0W-50 oil pours almost like water at room temperature, but still protects as well as straight 50 weight when hot. In other words, it has almost no noticeable change in viscosity through a wide temperature range.

Synthetic oil is a little weird though, in that it can protect your engine well enough without being quite as viscous as regular oil. So synthetic oil may be less viscous than regular oil with the same grade number. Regular 10W-40 oil might show about the same pressure on your oil pressure gauge as synthetic 20W-50. Also synthetic 10W-40 might be lower viscosity and show lower pressure than regular 10W-40. This tends to concern (disturb) some people who don't understand it. As long as your engine is in good condition, 5 to 10 psi lower on the gauge is normal with synthetic oil, and everything is still peachy. This is actually one of the advertising points for synthetic oil, that the lower viscosity can reduce friction and give you better fuel economy than regular oil (a little better).

Another problem with multi-grade oil in general (especially non-synthetic types) is that the viscosity index modifier additives tend to break down with heat and time. The viscosity then gets lower at high temperature with continued use, causing oil pressure to drop a little. This is why you may notice an increase in oil pressure with a fresh oil change. For this reason you may be better off using a multi-grade oil spanning a narrower range. That is, you might prefer 10W-40 or 20W-50 versus 10W-50, or only use the very wide range oil if you have a real need for it (like where temperatures range from 100dF to -40dF).

Today you might also find 15W-40 oil available. Maybe that's just another sales gimmick, supplying an additional product to occupy more shelf space to catch your eye on impulse. But in some locations 15W-40 may be available when 10W-40 and 20W-50 are not. I see this as a reaction of the retailer consolidating product lines to reduce shelf space requirements, especially in smaller stores (or at the "modern" self-service gas station). Fear not, as you should have no problem using 15W-40 oil in your MG.

Whatever the race car drivers are using you can totally ignore, as it has very little to do with ordinary engines and street driving. So don't be conned into thinking that racing oil will be of any benefit at all for street use.

The synthetic oils are also too damn expensive to ever be economically justified, except in special applications. I think a new Corvette or Viper might come from the factory with synthetic oil installed and specified exclusively, but other "real" cars still use oil which is considerably less than 100% synthetic (and actually affordable for regular use). The new car manufacturers are not dummies when it comes to economics. If the more expensive synthetic oil would return its cost difference in reduction of warranty repairs, it would be in every new car built. Similarly, synthetic oil will likely never return its large cost difference in reduced maintenance or longer life for your MG engine.

Because of the expense of the synthetic oil, there are now available "synthetic blend" motor oils. These are commonly about a 50/50 mix of regular oil and synthetic, and are priced accordingly. They also fool a lot of people into spending more money unnecessarily. What very few people seem to know is that regular motor oil these days is already about 25% synthetic, no matter which cheap brand you might buy. So the higher price you might pay for 50/50 blend is paid to increase it from 25% to 50% synthetic. Once you understand that, you might realize that it's just a marketing hype to grab your money, while still being nothing like 100% synthetic oil. Everywhere in a free market the shelves overflow with multiple and slightly different copies of similar products, with various manufacturers competing for more shelf space to catch your eye. Once you figure out which 10% of the products are a good deal, you can ignore the other 90%.

Back in the day, when we had to use 30 weight non-detergent oil, if you were real diligent you might extend engine life from 80,000 to 100,000 miles with frequent oil changes. Modern motor oil (the regular type) is so much better by comparison that you might expect an MG vintage B-series engine to run about 150,000 miles with no oil related problems. The engine life ends when the valve guides or cylinder walls wear out, or when it needs a valve job because of burning and wear of the valve seats and valve heads, and/or high oil consumption. If you don't abuse the engine (like running it out of oil or running it 7500 rpm for autocrossing) the crankshaft bearings might be nearly like new after 150,000 miles of running, and the camshaft and tappets should likewise last at least 150,000 miles.

If you use exclusively synthetic oil (after initial break-in) you might extend engine life to 200,000 miles, or maybe even 250,000 miles. But the much higher price of synthetic oil is cost prohibitive. I can build a second engine for about $1000-$1200, and run two engines 125,000-150,000 miles each on regular oil, for less than the cost of synthetic oil alone if you were changing synthetic oil every 6000 miles (for 250,000-300,000 miles) Maybe more to the point, if you don't drive the car enough to put more than 150,000 miles on it for the rest of your life, there is no cost benefit at all to extending engine life by using synthetic oil. In that case the increased cost of synthetic oil would be all out of pocket excess expense with no benefit at all. And it will NOT increase fuel mileage much, at least not more than 1% or 2% tops.

Barring non-detergent and single weight oil, you can use any multi-weight detergent oil you like in your MG, as long as it spans the 30 weight grade. 10W-30 will protect your engine in the hottest weather as well as original vintage straight 30 weight (better actually), and the engine will start very easy in winter. 20W-50 may give better protection and slightly increased life running in hot weather or working hard (like trailer towing or autocrossing), and the cost difference may be fairly small and tolerable. For a nice compromise, 10W-40 oil works well all year round for normal driving, protects well in scorching dessert temperatures, and will allow easy starting in sub-freezing temperature.

For many years I used 10W-40 oil all year round in everything I owned, from family sedan to pick up truck to sports cars to lawn mower engines. That sure makes inventory easy, and no seasonal oil changes required. I even ran autocross and trailer towing with 10W-40 oil in my MGA, from restoration and engine rebuild at 150,000 miles up to the next 100,000 miles on the same engine. In fact I didn't like using 20W-50 for competition, because the higher viscosity gives higher internal engine friction (especially in the crankshaft bearings) and robs a couple of horsepower at full chat. It can also degrade fuel economy slightly for highway cruising.

Some new cars specify 5W-30 oil for less friction and a little better fuel mileage to meet the government CAFE requirements. But if you read the owner's manual you may notice that it is allowed to use 10W-30 or 10W-40 oil, and your engine will return the favor with significantly longer bearing life. NEVER put 5W30 oil in a vintage MG engine. The older engines are not designed to tolerate the thinner oil. It requires a design change and more precise machining to reduce crankshaft bearing clearance by half from a nominal 0.001 inch to about 0.0005 inch. Using 5W-30 oil in an MG engine will dramatically shorten life of the crankshaft bearings, as well as dropping hot idle oil pressure significantly.

For me, if I concede to change the crankshaft bearings once in engine mid life (around 60,000 miles), I can abuse it all I like and it survives nicely on 10W40 oil until the piston rings and cylinder walls wear out. The indication for time to change the bearings is when hot idle oil pressure drops from 40 psi to 20 psi. Then installation of new bearings restores the oil pressure like new. If I never ran it over 6000 rpm It would likely never need new bearings (until the next scheduled engine overhaul).

So my recommendation for the average Joe is to use 10W-40 oil in an MG, and change it every 4000 miles or at least once a year, whichever comes first. If the car sits outside or in unheated garage with large temperature swings and high humidity, then change oil at least twice a year (even you don't drive it much at all), because it will accumulate water condensation and strange acids in the sump. Inside the valve cover condensation appears as emulsified oil and looking like shaving cream. If you see this white gunk in your engine in spite of regular oil changes, then you might look for a coolant leak past the head gasket, or a cracked cylinder head allowing coolant to leak from the water jacket into the oil sump.

Change the oil filter with every oil change, just because it's cheap and easy, and you won't forget, and it gets out another 1/2 quart of used oil. Otherwise a new oil filter with every second oil change is enough (if you can keep track of it), as the oil filters don't really get very dirty using modern detergent oil. If you drive exclusively on dusty gravel roads, then change oil as often as every 2000 miles and give it a new oil filter with every oil change.

If only 5% of your driving is on dusty roads, don't worry about the oil. With an MGA the larger problem with dust is ingestion though the air intake to wear out the top piston rings. Better air filters are a good investment for the MGA if you drive in dusty environments. If you ever drive on gravel roads, I highly recommend installing K&N air filters (see web site for details).

Buy whatever brand oil that is cheap, buy it by the case if it's cheaper, at an auto parts store or department store. Buy the house brand if it's cheaper. Most off-brands are manufactured by the big oil companies and packaged with the distributor's brand label. NAPA brand oil is made by Valvoline. K-mart house brand is bottled by Havoline. Wareco service station house brand is made by Phillips. And on goes the list ad-infinitum. No one is allowed to sell garbage oil any more. Even re-refined oil has to meet the same minimal functional requirements as any new motor oil. The largest consumers of re-refined oil these days are over the road truckers who use a lot of it and appreciate the slightly lower cost. You may never even know where to buy the stuff, as there is very little demand for it in the general consumer market.

I was working in a service station in 1968-1969 when the new oil came out to change the functional specification on 10W-30 oil from SC to SE (I think they skipped SD). We all thought it meant "Service Extreme", as the functional test requirements were indeed obscenely extreme compared to the auto makers requirements as little as 10 years earlier. This is when I was still using re-refined non-detergent 30 weight in my MGA and changing oil and filter every 2000 miles (which I learned as a farm kid running engines in dusty environments). It was a dire shock to me (price wise) to learn that I had to use 10W-40 oil in my new 1969 Austin America.

By now oil has progressed through SF, SG, SH, SI, and SJ specifications. If you look on the back of a bottle of oil today you should find "Service SL/SJ", and anyone selling oil has to meet the same stringent functional requirements. Bottom line: Use whatever oil is cheap, and you can't go wrong. Sometimes life with an MG is just simple. (Pretty often actually).

Barney Gaylord
1958 MGA with an attitude (and 340,000 miles)

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