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DR. Bolens
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My projects take longer so I enjoy them more...
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Here is my experience with Synthetic in a newer K301 (1990's longblock) - I ran NAPA 15w50 in it for 2 seasons. I did notice that as hours of use went up the oil usage went up but it was nothing significant. Moved back to straight 30W for air cooled and diesel engines and have not used a drop.
 

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I'm not sure about using a sin. 10W30 but I know that Amsoil makes a synthetic specifically for small engines that spec 30w oil. I have some of it here but haven't changed it into anything yet.
 

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Discussion Starter · #6 ·
Thanks for the replies. Everything I have switched over to synthetic just seems to run better. I'm not sure how an older engine with looser tolerances would handle it though.

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Discussion Starter · #8 ·
If your adamant about it, I would change the oil after a short amount of run time, just in case, to clear out what didn't come out the first time and ended getting mixed with the synthetic.
I'm not really adamant about it. I'll prolly just stick with conventional oil. I agree that would be the best way to switch over though.

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:thumbs: I'll chime into what is probably a huge and contentious subject. :D

I am a big fan of synthetic. Always have been, but I use non synthetic in my k-series.

I used mobil-1 synthetic in my dad's ford LGT (kohler k341) when he let me use it for several years. I then got into old cars, and learned that a lot of old car guys stay away from synthetic, for two reasons- 1. The synthetic has a tendency to loosen old seals, so things that weren't leaking might start leaking, and 2. (more importantly) Zinc levels (ZDDP). Back when engines had flat tappets/cam shafts, engine companies learned that at about 1200-1500ppm zinc was a good level to prevent cam / guide wear. Much more/or less- and wear increased. Especially with less.

As cars progressed, many engines switched to roller cam assemblies, so direct metal/metal wear was reduced. Also, with catalytic converters, came concerns that the Zn would clog the CATs, so companies dropped zn levels significantly. It doesn't matter in new cars, but many feel older engines can benefit from the high zinc levels. From what I understand, the zinc is a sacrificial substance that coats the surfaces and degrades with wear instead of the metal. Many oils today have ZDDP in 800 range or less.

When I got my Kohler rebuilt by one of the prolific engine rebuilders who specializes in K-series, he told me to go with a brand of conventional dino that still had high zinc levels, because in his experience, oils with the lower levels were having problems with valve guides and such( I think it was valve guides, but I don't recall- but it was SOMETHING!). This was a direct observation from his experience. He flat out insisted any warranty he provided depended on me using that oil. I think it was castrol- but that doesn't matter, because even THAT oil has lowered it's zinc levels since he made the recommendation.

In my classic car, as much as I have WANTED to go synthetic, I have stayed with conventional DINO oil. I use a USA made racing oil- Brad Penn. It has the high zinc levels and is held in high regards. Since I usually have some leftover Brad Penn around (expensive- $9 quart, but not much worse than Mobil-1 synthetic), I will put that in the engine when needed. Overkill in a garden tractor? perhaps.. but it is only about one quart.

As for my dad's tractor, he needed it back, and after about a year, it blew a valve guide or something. Was it because of me running low zinc oil? Probably not- who knows really- but I sure ain't gonna tell him!

Ironically, mobil makes a high zinc synthetic oil for motorcycles. Specifically- the Harley v-twin engine. Only problem is that it is 20-50 weight, which actually might work well if the engine is loose and worn in a Kohler.

I'm not pushing Brad Penn btw....I use the straight 30 weight brad penn in my K-series. It has the high zddp, is the recommended weight, and works well.

And one final study that made me feel better about not running synthetic. The New York City Cab company ran a study of synthetic vs. regular in it's fleet of cabs. Over a long term study, it found NO DIFFERENCE in wear between engines. That's about as hard core of a test as I could imagine. Interesting. Even knowing that- I still ideally would want a synthetic, but oh well....Perhaps if someone made a high ZDDP synthetic in straight 30... oh to dream! .

I will throw in a link to a car site I go to frequently, with a little background into this controversy (p.s.-your head will explode!)

http://forums.pelicanparts.com/porsche-911-technical-forum/367300-ultimate-motor-oil-thread-why-we-hate-cj4-sm-oils.html

...when looking at the first page recommendations, keep in mind the dates of when this was made. Some oils have lowered the Zinc levels since then.
 
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