Careful not to overthink stuff like this.
Pretty much any quality oil that has the right spec’s and changed as recommended will not be the weak point in your mowers life expectancy.

If it calls for Synthetic I use Mobil 1 and if not, I use Rotella in the correct viscosity.

quote:

Originally posted by Ripley:

quote:

Originally posted by .38supersig:
Does the 15hp engine have a pressurized oil system?

How does that change oil choice?

Most small engines without a pressurized oil system have a pin running off of the connecting rod or cam gear designed to splash or throw oil throughout the crankcase, the camshaft, and cylinder bore. These parts don't get oil until adequately sprayed after the engine has started running at full speed. The oil for these engines would (hopefully) have a higher residual quality and engine specific additives (I think that reflex/deflex 64 and shovelhead explained this better than I could have) for small engine use. Another consideration would be that the engine is air cooled and may have hot spots in the crankcase that hopefully are cooled somewhat by the oil bath. This type of oil would be designed with these things in consideration.

A pressurized oil system would start pumping oil as the engine is being started. Most of the engines now will not energize the coils of the ignition system before optimal oil pressure has been obtained. Automotive oils would work better in a pressurized system because that is what they are designed for. Plus the emissions aspect and fuel economy restrictions.

Yes automotive oil is 4 stroke oil and it (mostly) is suitable for use in a 15hp mower.

Where do you live, what engine are we talking about, how long does the engine run before you shut it off, and I can provide better recommendation. I have changed oil thousands and thousands of times in small engines. I used to have a small engine shop, and noticed some trends over the years. What works, what is adequate, and what doesn't work.

I will also add that boutique synthetic oil at $10 a quart or more is an outlandish waste of money. I'm always on the lookout for an oil bargain, and I almost always get my oil for 50 cents to $1.50/quart, to include high dollar synthetic and fleet/diesel oil.

Generally speaking, for a mower, I recommend the following:
-SAE30
-synthetic 10W30 SN car oil
-diesel/fleet oil 10W30 (Rotella, Delo, etc)
-diesel/fleet oil 15W40 (most are dual rated for use in gas or diesel engines, and have excellent additive packages)
-Kohler command engines ALWAYS get diesel/fleet 10W30 oil, nothing else


Brand doesn't matter. If its meets the spec, it meets the spec (SN plus). The Walmart brand SuperTech synthetic jug for $15 right now(great deal) is just as good as the $27 bottle of synthetic right next to it. They meet the same specs.

John Deere 10W30 and Kohler 10W30 are good oils. They are heavy duty fleet style oils, so likely they are just re-bottled Delo 10W30 or Rotella 10W30 oils.

quote:

Originally posted by bubbatime:
Yes automotive oil is 4 stroke oil and it (mostly) is suitable for use in a 15hp mower.

Where do you live, what engine are we talking about, how long does the engine run before you shut it off, and I can provide better recommendation. I have changed oil thousands and thousands of times in small engines. I used to have a small engine shop, and noticed some trends over the years. What works, what is adequate, and what doesn't work.

I will also add that boutique synthetic oil at $10 a quart or more is an outlandish waste of money. I'm always on the lookout for an oil bargain, and I almost always get my oil for 50 cents to $1.50/quart, to include high dollar synthetic and fleet/diesel oil.

Generally speaking, for a mower, I recommend the following:
-SAE30
-synthetic 10W30
-diesel/fleet oil 15W40

15.5 hp Briggs, has an external oil filter that I change annually, so it must have a pressurized oil system. Air cooled, Husqvarna model with a belt driven 38 inch deck with two blades. I live in SE Va, so summers can get very hot and humid. Not has hot and humid as New Orleans or Easely SC, but plenty hot enough. When I turn off the engine it stops immediately normally. But I rember one summer when it would deisel-run after I shut off the ignition. I don't know why it did that, nor has the problem returned, but it may have been exceptionally hot weather when it happened, I don't recall.

There is one thing that happened once, that I haven't mentioned, since it may not relate to what we're talking about. One summer I hired a mobile power equipment dude to do an everything maintenance job, and later discovered he didn't put enough oil in it. So when I ran it on a hot day, I noticed the engine was blowing lots of smoke, so I shut it off immediately and checked the oil. Sure enough that fellow failed to fill it with sufficient oil. That was the last time I hired a mobile tech. I never thought he would have done that because he came highly recommended and worked at Sunbelt Rental and maintained all the machines. The engine has never been the same since, so there has been some damage, but seems to runk OK as long as I keep the oil topped off, since it does burn some oil since that incident.

OK, based on that I would forget the synthetic. Your cylinder walls and piston are scored.

Stick with SAE30 or 15W40. Briggs even recommends 15W50 now. If your engine burns oil, I'd give that a try for an oil change and see how it runs.

Your engine is splash lubricated. Hardly any Briggs engines are full pressure lube, even the ones with oil filters. They have a tiny oil pump that just pumps oil through the filter.

quote:

Originally posted by .38supersig:

quote:

Originally posted by Ripley:

quote:

Originally posted by .38supersig:
Does the 15hp engine have a pressurized oil system?

How does that change oil choice?

Most small engines without a pressurized oil system...

Thanks,.38supersig, the hive delivers again.

I have a commercial walk-behind Toro. I got it because of its oil pressurized Kawa engine. It leads a horrible life mowing mostly a twenty degree slope yard, about two and a half hours a pop. Most riding mowers limit slope to fifteen degrees, the ones that can handle my slope are way beyond my budget. I've used the crazy pricey Opti oil because the local Toro/Stiehl dealer pushed it. It's not like I go through gallons of it and I want the mower to live. So far so good...

I used to go through about a typical mower a year. I'd have to figure which side the oil pickup was on and keep the mower tilted that way, pushing one way, pulling back. That was how I totally infested my yard with crabgrass, discharging it on up the hill.

I hear Mobile 1 on everything solves everyones problems. Life is so simple now.