VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Selection of the right oil for Flat Tappet engines

In case anyone is interested, here is a draft of a paper I put together, primarily for the Corvair groups, but the concept is
Selecting the right engine oil

I’m sure there will be additional questions that will arise or points that I haven’t explained to the satisfaction of some readers. Please send your questions to oil [at] asboman.com and I will answer them in the next draft.

Holy cow!! What a huge amount of work you have done to produce this document.

This looks like a PhD thesis on oil.

Great Job!

I will read it a few more times then make a choice for my cars.

Rich

Richard,

On page 14 of your paper, you note that you use CI-4 oil in your vehicles. Do you drive a diesel? I have done some internet research on this oil and every reference that I see talks about using this oil in diesel engines.

Thanks,

Rich

Wow, sometimes I have the opinion that some folks have so little real things to do that they flood the forums with:
INFORMATION OVERLOAD!!!!!!

By the way that includes
MYSELF!!!!!

i too use(and have used) oils designed for diesel engines for the past 30 years. CI-4 has enough zinc(ZDDP) that will enhance the life span of engines with flat tappets and non-roller rocker arms.mike

Very interesting paper. The people at the AACA site would welcome your posting this on that board.

I have used oils designed for diesel engines but only recommend such usage from new or near new rebuild and not in an engine that has a lot of miles on it.
There seems to be a higher detergent component that removes any carbon build up behind the compression rings that increases ring blow by neccesitating a earlier rebuild. It also prevents any sludge build up in the rest of the engine even after 80,000 miles but does neccesitate more frequent oil and if fitted filter changes.
Tony

Personally I have a several diesels several gasoline, several natural gas, and 1 propane engine.
A fully formulated CI-4/SL with Group II base oils or better covers everything you could want. The only exception is long life of the catalytic converter, of which I have none, and then only after a few hundred thousand miles. That situation also depends on the NOAK evaporation of the oil used, but a CI-4 is limited to 13%. The good group II oils are around 10% or less, while a good synthetic will be closer to 7 or 8%. Less evaporation, less contamination of the cat. converter.

The extra detergent and anti-wear does not hurt a gasoline engine and really helps rubbing surfaces. As long as SL is on it, it is safe for Gasoline. Exceptions would be railroad type Super-high detergent with a TBN of 14 to 17, designed for engines where you almost never change oil, just keep adding.

The old wives tale that a good oil cleaning up those grooves is detrimental to the engine is false. You need to clean them up to get the rings functioning properly and allow the pressure to get behind them and push them outwards. You might have one oil change of smoke or consumption. Then you will be amazed at the improvement in compression and reduction of consumption.
As I say in the paper, I do it every day.

BTW, I've updated it, adding further clarifications based on feedback.

And I'll sign up over there and post it. Maybe I'll need that forum when I track down the wooden spoked car that I was told about last week sitting in a garage in the middle of nowhere.

Here is an updated link that will take you first to an Intro and comments as it gets updated before taking you to the paper.
Selection of the Right Motor oil for Flat Tappet Engines