PART 1: Today's topic seams to be motor oil related. I am a NASA Engineer at Marshal Space Flight Center in Huntsville, Alabama. My field of work is Tribology which is the study of friction, wear, and lubrication. In our spare time, our group collects and tests different motor oils using the Shell Four Ball tester. This tester tests the extreme pressure properties of oils. These areas in a motor are cam to lifter contacts, valve stem to guild, and piston skirts. Over the years we have found synthetic bases oils to out perform mineral based oils by a large margin. We test the oils new, after 1000 miles, 2000 miles, and up to 10,000 miles. In a nut shell, we found that synthetic oils have better wear properties after being run 10,000 miles then mineral grade oils new. Which synthetic do we use?
First any you will benefit from any synthetic, but we use Mobil 1. Mobil by far puts more research dollars in motor oils then any other company. They are also aggressive in racing.
Other notes on motor oils.
Do not run a multi grade oil (10w-30) more than 1000 to 2000 miles - depending on your driving habits. This is because a 10w30 oil starts its life as a 10 weight oil and large polymer chains are added to get the 30 rating. These chains break down very quickly which produces small chains with an open electron charge at the ends. These ends attract grim and form sludge.
Do not run synthetics in a new rebuild. A new engine needs the added friction allowed by mineral oils to set the rings properly. Chevy found this out on the corvette. These cars came from the factory with Mobil 1 and owners brought them back because of smoking and oil consumption (rings did not seat). Run a good single weight oil for the first 2000 miles. We found Havoline 30 to be a good mineral oil - in fact we use it for our standard.
The reason Mobil 1 can safely be run for 10,000 miles is because the additive package is well engineered to isolate grim and hold it in suspension. This also is why Mobil 1 is expensive. You know - you get what you pay for.
I know there are a lot of questions on motor oils. You can e-mail me for more information or search the web for more details on synthetics. Your Roadster deserves the best - run synthetic oils.
Part 2:
I listed multi grade oil break down at 1000 to 2000 miles. This is for the junk oils found at circle K for a dollar. A good name brand oil will last 3000 miles without too much break down. This is for mineral grade oils - synthetic oils meet government viscosity tests for ratings without adding thickeners like polymer chains.
Guys here at work run synthetics in motors that have 140,000 to 170,000 miles on them without any more oil consumption them normal. I believe that you will get a slight increase in consumption in older motors because the synthetic are very slippery and can get by old rings easier. In these cases going to a 15w-50 may help, but this is not a reason not to use synthetics. Older motors need the extra protection. At running temperature a synthetic will maintain its viscosity, where a mineral oil viscosity is DRASTICALLY REDUCED.
A test on how well synthetics work at different temperature can be done in your home. Get a quart of your favourite mineral oil and a quart of a synthetic. Put a cup a each oil in a glass or paper cup and stick in the freezer over night. In the morning try and pour the oils out. Next test: DO THIS OUTSIDE. On an old camp stove put a ΒΌ of the synthetic oil in an old frying pan and put it on the stove on the highest heat setting. Cook for 30 minutes. Now cook your oil for 30 minutes. At this point you will see why you cooked the synthetic first. As the oil cooks pour some out to see the changes in viscosity between the oils.
Part 3:
The question of change intervals and synthetic oil has come up. As a side at work we run oil tests using the Shell Four Ball test rig. This tester was developed by Shell oil to test the extreme wear properties of motor oils - cams, piston skirts etc. It consists of three, = inch balls held in a triangular pattern in a cup with oil heated to 165 degrees. A fourth ball is lowered to the center of the three balls and loaded to 40 Kg. The ball is then rotated 600 RPM for one hour. After the test the wear scar is measured on the three stationary balls. The bigger the scar the lower the extreme wear property of the oil is. We use Havoline 30 wt for a base line. We use this oil because engineers from the past liked this oil, so we have a large data base.
Looking at data shows new Havoline 30 wt has a wear scar of .0165 inches. New Mobil 1 has a .0145 inch scar. May not seem like a lot of difference, but it is. Havoline 30 at 3000 miles has a wear scar of .020 inches and Mobil 1 at 4000 miles has a .0164 scar. Remember - the bigger the badder. 3000 miles is as long as anyone was willing to run Havoline 30 wt, so its data stops here. Mobil 1 at 6000 miles is .0167, at 8000 miles is .0188, and at 10,000 miles is .0194. So, at 10,000 miles Mobil 1 has better lubrication properties in the critical areas in your motor then a good 30 wt. All mineral oils follow Havoline pretty close - major brands. Some of the brands have a .020 wear scar new. Multi-grades generally have a larger wear scar as well. This data was from a 5.0 Ford Mustang. Every motor will be slightly different, but not much.
So, synthetic can handle long run intervals. But, that is part of the story. You have contaminates to deal with. This is where the additive package comes in play. This is the expensive part of oils and the reason synthetics are high priced. Because of the long run intervals of synthetic, they must have a vastly superior additive package - and they do. Proof of this is to take 3000 mile dino oil and look at it in a glass jar - then do the same for Mobil 1. The Mobil 1 will look new compared to the dino oil. I run Mobil 1 in my new cars to the longest manufactures oil change interval - usually 7000 miles. This will keep the warranty happy. In my Roadster I change it once a year regardless of mileage. It run my Roadster about 5000 miles a year. Most people at work run synthetics and do the same. We have a bunch of cars in the lot that have over 200,000 miles on them and going strong. I (my wife) never keeps one that long.
I run 10w-30 Mobil 1 in my new Roadster motors (after break-in). Older motors get 15w-50 because the tolerances are larger. Because synthetics don't thin down like mineral oils do at temperature, I would be careful running 15w-50 in a motor with a high volume oil pump. By doing so you may run into cavitation problems - oil gage jumping wildly. Drag racers experience this often at high RPM. Drop a wt and it will clear up.
I checked the auto parts stores last night and could not find a zero wt Mobil 1. It was about 2 years ago they were talking introducing this oil, so apparently they have in some markets. I stand corrected.
Testing another "magic" oil additive today. It looks and smells like linseed oil! This should be fun. Additives are another subject all together. Another day, but never tested a good one - none- zip - zero - don't waste your money.
Sorry for being soo long. I like synthetics (obviously). If you have been to the conferences, seen all the tests and data, and read the lubrication journals you would run nothing other then synthetics.
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