How bad can Too much oil be? & are SL SJ oils OK to mix??

Not open for further replies.
Jun 19, 2003
Brampton, Ontario, Canada
Hi, I searched for it and could not find an answer: what does acctually hapen when you put 0.5 qt of oil too much [Confused] And since I am new to this board I have one more question: I've got two litres of Agip semi-synt 10W-40 SJ about a year old I went get two more litres for my next oil changes but this is already SL rated, should I buy all 4 bottles of SL rated stuff and keep the SJ for lubricating hinges, latches and stuff??
In most engines, 1/2 quart over will be just fine. If it really was slightly overfull, it would just burn off rather quickly and level out. Most engines have a bit of leeway here though, especially if you've got an engine that takes 5 quarts or more, then that 1/2 quart over is only a 10% increase in capacity. LS1 engines can take 1 to 1.5 quarts more than their capacity, GM even tells Corvette owners if they race their cars, to add an extra quart more oil.
Dominik, I won't sweat mixing the SJ with the SL. Especially since you are using the same brand and grade. I did it with Mobil 1 5W-30 and ran it for 5,000 miles with no noticable problems. Never used any oil and ran like a charm. If you were mixing two totally different oils then I probably wouldn't do it. But that's just me. Other people on this site have mixed up some real witches brews using various oils [Big Grin] . Whimsey
On small 4 cyl engines the 1/2 is at the upper limit. I personally would drain a little off. No problem with mixing oil SL/SJ
Originally posted by Dominik: Hi, I searched for it and could not find an answer: what does acctually hapen when you put 0.5 qt of oil too much [Confused] --- Snipped----
Well I'm no mechanic but I have had the experience of it could (in some engines) usually over time ( a long time ) blow a seal (rear Main), and if left un repaired, the front too. Most cars you can get away with 1/2 quart, but You should not do it all the time unless You want to take a risk. A friend of mine has always had about 1Qrt over because he goes to the quick-lube places and they always overfill... He has either 244 or 264K no leaks no problems. Toyotas (tacomas at least) will usually allow you to overfill a little. I did for 300 K miles or so and my Valve cover and oilpan were starting to leak, but then again the pan was leaking with it new at the dealer. But in answer to the question: Do what the MFG suggests, and you'll likely have no problems because you took matters into your own hands and did otherwise. Also, IMHO I would assume that the larger engines would more than likely allow for a little more overfil than say a 4 banger. Cheers!
Domonik, As you have already heard...half a quart should be fine. [Smile] Oil will airate when too much is added (usually a quart or more overfull)as a result of the crank and rods splashing in the oil...airated oil has greatly reduced film/shear strength. If you run into this situation drive nice and easy until the overfilled condition can be corrected to prevent the possibility of increased wear. [Frown] If I remember correctly...airated oil will also tend to get hotter which could cause reduced oil life also. Someone with more experience might be able to confirm. [Wink] SL/SJ is OK to mix...most oil already meet new oil specs before manufaturers require it! Just have to use up all those old labels/containers. [stretch] [Cheers!]
Not open for further replies.