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Here is a link that might be useful: All about oily things

I have a JD325 with a Kawasaki 18hp air-cooled engine. It says to use SAE 30 or 10W-30. I went with Mobil 1 10W-30. I average about 50hrs on the tractor a year, only using it in warm weather. I have about 250 hours on the engine, and it does not use any oil between changes (once a year). I chose synthetic because of the high temperatures in the hot summer months. Some engine manufactures suggest going with synthetic if you elect to go with multi-viscosity oil, which you have done. It would seem like the synthetic oil would have been less likely to burn it at high temperatures. Charles Ranheim

"It would seem like the synthetic oil would have been less likely to burn it at high temperatures"

He has an old engine with several hours on it. Sym is thin, doesn't matter if it is better oil or not. I would also point out that all the Mfgs. Owner's Manuals that I have seen recommend the same change period for sym. as dyno.

Walt Conner

Perhaps I misunderstood, but I thought some manufactures suggested going with synthetic if you decide to go multi-viscosity in order to reduce oil consumption. I believe in the original post, the user went from conventional multi-viscosity to synthetic multi-viscosity. This is why I made the comment I would have thought the synthetic oil would have burned less than the conventional oil. Charles Ranheim

In theroy I agree, older engine with unknown maintenance history, thinner oil may = oil consumption. IMO you have two choices, go back to a 30 W oil or keep running the syn maybe it will seal up. As a rule IMO you don't want to wait too long before switching to syn. Not knowing your oil change intervals the syn maybe too thin for a half wornout engine. Not a problem if you are willing to just keep adding oil as the engine uses it. IMO it wood be better off with syn oil even though it uses some between changes unless you develop a crank seal leak.

I also believe that changing the oil atleast three times a year regardless of hours would be alot better than manufacture hourly change requirements regardless of what oil you use. Depending on usage this could be two years or more going strickly on hourly use. IMO this is way too long and increases wear and wears engine out early. I have never worn out a small gas engine. but I change my oil often.

74 tiller going strong, 84 dynamark pushmower still no smoke runs like new, 89 vangaurd 160 psi of compression still, or maybe I got lucky I wouldn't put syn oil in these engine due to the age and hours on them. All of this is of course MY OPINION, other may and usually disagree

I am not sure I would consider my tractor all that old. After this season it will be 5 years old.

I was just surprised that it never burned any regular 10W30 oil but now it does burn through synthetic 10W30 oil. The only thing I can think of is that Pennzoil synthetic oil is crap.

My next question is, what happens when the oil is burned. Is the only problem, the using up of oil and having to re-add some more or does burning oil cause other engine or exhaust problems?

Briggs' rule on oil consumption is 1oz/hr/cylinder. You are well within that. Your engine, as do many small engines, likely just consumes some oil. Changing back to dino 10w-30 will likely not make much difference.

In terms of 30w and 10w-30, the 10w-30 tends to evaporate more than actually get burned away, thus the recommendation to use syn 10w-30 should you want to use that weight of oil.

Briggs, by the way, now endorses 10w-30 syn oil as their oil of choice over the old standard of 30wt dino. It has been measured to drop the overall engine operating temp by 20-degrees if I remember correctly.

The dabate on changing older engines to synthetic occurs frequently on car forums. The consensus seems to be that the synthetic does a much better job of cleaning the internal components, and that this process does, in some cases, result in some added consumption. This added consumption is usually reported as a temporary condition that clears up as the internals get fully cleaned. It is this same cleaning action that is sometimes pointed to as the "cause" of leaks on changeover, while what has really happened is that the crud that was hiding/plugging a previous leak has been removed. The syn. didn't cause damage, but did reveal weaknesses that already existed. In my case, I change all my motors to Mobil 1, at whatever age I get them, and have never had consumption or leaks. I always do see a much cleaner interior, after a period of use.

That's pretty interesting. Thanks a lot guys.

After having many engines apart that have seen the same type of use, (but different types of oil), I'm convinced that the ones that have had synthetic oil appear *cleaner* not so much because the oil is doing a better job of *cleaning*, but because much of the discoloration on internal parts, much of the caked on gunk that's baked onto surfaces, etc. simply doesn't occur as much with synthetics because they handle heat stress far better than conventional oil does. Look in the nooks and crannies where oil sometimes collects and sits, and/or areas where the most heat is....an engine that's had synthetic oil in the crankcase will look as if it has accumulated half the running hours....or less.

The oil isn't only doing a better job scrubbing things clean, it just isn't deteriorating/breaking down/baking on as much.....so there isn't as much gunk for it to *clean up* in the first place.

That said, use whatever makes you happy....manufacturer-approved of course.

;-)