Confused on oil

I run 15W-40 Delvac in the tractors, I want to run a heavy duty synthetic in my mowers. I am confused.

What should I use?

Use whatever ya want. Iron doesn't care one way or another.

Allan

What kind should I use indeed!
Any subject besides motor oil I would say you can't stir up the hornet's nest again this soon after the last go around. At least you will have plenty reccomendations to choose from.

Iron does care if it has a flat tappet cam. Modern off the shelf oil, other than diesel rated, does not have enough zinc to protect flat tappet cam's.

My confusion is over the synthetic in an air cooled engine.

I do not understand the different ratings.

Unless your mowers are radically tuned racing mowers, they will thrive on any modern oil 10-30 20-50 or 15-40 diesel. The spring pressure and wear properties of mower engines are modest. Synthetic will do nicely. A hard running hot day air cooled engine with synthetic oil is happy. Modern synthetic oil is far more stable at high temps than conventional oil. Jim

Thanks Jim

(quoted from post at 22:35:10 04/05/14) Iron does care if it has a flat tappet cam. Modern off the shelf oil, other than diesel rated, does not have enough zinc to protect flat tappet cam's.

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Modern diesel oil for 2007 and later EPA emissions is low zinc, low ash and doesn't protect flat tappet cams and followers either.
Have a look, they are roller cam engines.
Use a pre 2007 diesel oil.

Modern OHV air cooled engines LIKE syn oil, 'cuz it's less prone to breaking down from heat and sticking a valve, which leads to the pushrod falling out of place and getting mangled.

Briggs and Kaw engines, for sure.

I don't bother with confusion, I have four tractors, two balers and numerous other machines to maintain and operate. The mower gets new synthetic oil, new filters, grease job and blade's sharpened in the spring. Unless my daughter or one of the grandkids manage to break it - that's all the attention it gets!!

First -define what you are calling "synthetic." Many oils sold as "full synthetic" in the USA have NO synthetic content at all. Many are based on pure petro from the ground. Some posters claim that "synthetic" oil has higher heat tolerance. Again -NOT true for many. In fact, many pure petro oils from Shell have a higher "flash point" that most of the consumer oils sold as "full synthetic." Probably one of the best oils around are those with high anti-wear additives like ZDDP. Briggs & Stratton sells small engine oil with more protection that just about any oil sold for automotive use. Back to my point - even when oil IS truly synthetic - it has absolutely nothing to do with "better" lubrication. True sythetic oil has a high heat tolerance well over 400 degrees F and a wider viscosity range relative to air temps. Standard petro-based oils tend to have "flash points" from 380 to 430F. True synthetics (often sold as racing oils) can be near 500 degrees F. That's why our military used them on jet engines.

Again - lubrication is about the proper viscosity, temp range, and additive package. Not about being from petrol, coal oil, or any blend made in a test tube.

By the original definition - synthetic oil is/was oil made from a non-petroleum base. MANY oils sold in the USA as "synthetic" are made from a 100% petroleum base. Pure marketing BS as I see it.

Adolph Hitler used true synthetic successfully during WWII due to lack of access to petroleum. It was found that the new synthetic oil had far better heat resistance then petro oil (Flash Point). The US military copied the product and used it in jet engines (where heat was a problem). Years later - a military guy marketed the stuff to civilians as "Ammsoil." He was jet pilot and commander Colonel Albert J. Amatuzio.

Now? There are many oils sold as "full synthetic" that give less high heat protection then many conventional petro oils. I don't see the point?

Next time someone tells you how much they love their so-called "synthetic oil" - ask specific questions.

Note that true synthetic oil is still available and mostly used in off-road and racing. It still has that very high flash point and stable viscosity. Shell Rotella T conventional oil has a higher Flash Point then many oils sold as "full synthetic." Here are a few Flash Point ratings of various oils. Highest to lowest.

Briggs & Stratton small engine oil - 5W-30 synthetic - 464F

Ammsoil HD/Diesel/marine 15W0-40 synthetic 464F

Shell Rotella 40W conventional - 460F

Shell Rotella 30W conventional - 450F

Chevron Delo 15W-40 conventional - 446F

Deere 0W-40 Synthetic - 446F

Amsoil 3000 synthetic 5W-30 - 439F

Deere 15W-40 Conventional - 437F

Shell Rotella T 5W-40 synthetic - 432F

Shell Rotella 15W-40 conventional - 415F

Valvoline Premium Blue synthetic 5W-40 - 392F

Castrol Syntec synthetic 5W-30 - 392F

Castrol Syntec synthetic 10W-30 - 392F

In the case of the original poster here - Briggs &
Stratton sells one of the highest ZDDP oils on the
market for small engines. He doesn't have to look
hard for a good small engine oil made for flat
tappets and high heat tolerance for air cooled use.

Briggs & Stratton small engine oil - 5W-30 actually
a genuine synthetic and a temp flash point of 464F.
Also three times the ZDDP content of most modern
auto oils.

I keep it simple. The diesels get Delvac and everything else from the F250 to the snow blowers and mowers get Mobil1.

Synthetic is a good choice for air cooled engines.

Air cooled engines don't typically have a thermostat, so they run at a much wider operating temp range than water cooled.

They also have "hot spots", areas of intense heat due to design flaws or dirt/grass caking in the cooling fins.

A synthetic oil with a high flash point will help prevent the oil from burning in those areas.