Synthetic motor oil in your lawnmower??

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May 18, 2009
Sarasota, FL
I posted this in this forum so that more people would see, because I'm sure a lot of you have thought about this too! I picked up my lawnmower from the maintenance place.. it was just easier since they have the air filter, they know what plug it uses, etc. So I checked the oil in it today and it was overfilled by a LOT! WWF This gets me upset.. do they not even check?? So I took all that oil out, put it in an old Mobil1-0w40 bottle, and refilled it to the proper level with PP 5W30 and RTS 5W40 (it calls for SAE30) hide ..the oil I took out will be for toping-off. Anyone else here put synthetic in their lawnmowers?? Any complications?? Mine feels "stronger" so far but could just be me. That's when I checked it: PP 5W30 in! Old-new SAE30 lawnmower oil in the Mobil bottle, don't worry.. now I put a label on it so it won't get confused with my other Mobil-0w40s.
I use synthetic oil in my mower and snow blower never had any issues. The mower gets the old, stray, synthetic oil orphan quarts, it runs great.
I thought about this too... Since the mower works in a VERY dirty environment, and it has no oil filter... is it a good idea to just put in the used synthetic from my cars?? I change it very often anyways because it gets so dirty in the mower!
A few years ago I put RP in my snowblower and briggs 3.5 HP. Thought it would be perfect for AC engines and the cold environment of the blower. Both leaked - the briggs leaked a LOT and the head and side cover came loose. Went back to tractor oil or orphaned bottles of PCMO ( 530/1030) and no problems , no leaks no falling apart. I think the mower had about 8 years of sevice on it when I put the syn in. I use ashless 2 strok oil at 200/1 in the gas ( though briggs says NO!) and have NO oil usage through the season and engine still runs NEW. I would not discourage you from trying syn though, and if it uncorks - dump it go back to conventional or try High Mileage syn. Our Loyale 1.8L subaru also leaked like crazy on syn in 91. That was "real" syn.
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Those motors will run with any kind of oil period. I usually buy a quart of diesel truck oil, and run that in there for the season. If you read the book, it takes like 10 ounces of oil or something, I forget the exact, but its a little less than a quart.
I've been running Amsoil 5W-30 in my push mower since I bought it new in the summer of 2008 (well, after using the oil that came with the mower). I use the same oil in our Murray riding mower which was purchased new in 2003. It is also doing great with it. I was a little worried about the recent reduction in ZDDP in these oils and may consider switching to Amsoil's dedicated 4-cycle small engine oil, but probably won't as valve tappet issues don't seem to be a problem with these.
I have a Toro with a Briggs engine. I have had it since June and run it on whatever Synthetic I can find, typically a 10w30. It makes sense as it is an air cooled engine. The only interesting story that I have about old lawnmowers is about my Father. He had a 10 year old lawnboy that started smoking and burning off oil to the point where it would give him a headache while mowing. He tried a high mileage oil and it solved the problem. He now has a Toro with a Kohler engine and he got rid of his lawnboy when some parts on the deck broke and upon dissassembly he figured out that the transmission was on its last legs. A diesel or full synthetic, or a full synthetic diesel, is the oil to go to in these small air cooled engines. Although they run on anything, it is good to keep them clean and efficient as long as possible.
I think it is more like twenty oz. Not a whole lot. These cheap air cooled engines are remarkable for their ability to soak up abuse and just keep on running.
Briggs and Stratton now recommends synthetic in all their engines. I use 10W-40 synthetic motorcycle oil in my John Deere with Kawasaki engine. It now has 1862 hours. I use 10W-40 synthetic motorcycle oil in my John Deere with Briggs and Stratton engine. It now has 52 hours. I use 10W-30 MaxLife synthetic in my little 5 HP Briggs and Stratton trim mower. It now has a best estimation of 64 hours(no meter)
My dad used M1 10w30 in lawnmowers before the manufacturers permitted anything other than SAE30 in Florida. It worked fine. I don't know how much life was added, because most lawnmower engines go for ages with basic oil changes.
Even though I carefully measure the oil going into both my lawnmower and snow blower with a glass measuring beaker, the dipsticks always show that the engines are overfilled.
Originally Posted By: Johnny
Originally Posted By: MrWideTires
PP 5W30 in!
That's where you pour the oil in? That looks like the gas tank on my mower.
No.. look a little to the left of the oil bottle, that's where the gas goes in.. it's open too. I was filling up both the gas tank and oil sump!
MrWideTires, For the last few years I used Rotella T-SYN in everyhing I owned.. three cars, two motorcycles, a lawnmower and I even saw my dog drink some once. I would buy it 5 gallon pails at the farm store for under $3/quart and all was and is well.
Originally Posted By: ARCOgraphite
Gas tank is in the rear. Just dont let your wife gas up the mower;)
What wife? You mean one of the girlfriends? getdown
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