Mixing Motor Oils

[KELLY88]

Does it matter if you mix different types of motor oil? My brother's Cadillac developed a small oil leak, went unnoticed until the oil light came on. He was afraid to drive it until he got some oil it, not a bad thing. We had some cheap conventional oil in the garage but I told him not to use it, to get synthetic like his car was already running. I honestly didn't know the answer to the question but decided it would be best to err on the side of caution. So the question really is this: is it ok to mix synthetic oil with conventional oil if you're just topping it off? Also is it a bad idea or does it not matter when it comes to the oil weights? Would be nice to know for future reference.

 

[fastpakr]

Mixing types of oil is perfectly fine. Obviously, you'll have to keep in mind the inherent change to the weight if you're mixing a portion of a lighter or heavier weight, but other than that nothing will happen.

 

[LearjetMinako]

Its perfectly fine to mix different types of motor oil. Weight grades don't really matter too much, just try to stick the last number for weight. But its still better to put in a 10-40 weight than run the engine with low oil, and then change the oil to the correct weight.

 

[85_Ranger4x4]

Wrong oil is better than no oil anyday.

 

[KELLY88]

Good to know. Much thanks everybody. Just didn't want to make a $5 mistake and blow a motor.

 

[LearjetMinako]

Good to know. Much thanks everybody. Just didn't want to make a $5 mistake and blow a motor.

The $5 mistake would be to not add any oil.

Anyday, just ask the TRS. Somebody on here is bound to help.

 

[OilPatch197]

What about detergent oils? Are they compatible with non detergent oil?

 

[94STXRanger]

uh mixing conventional and synthetic cant be good...

 

[2manyfords]

uh mixing conventional and synthetic cant be good...

Why?

Thats what semi synthetic is.

 

[MAKG]

It's best to keep to the same viscosity if you can, or a LIGHTER one if you can't. Too heavy an oil is a BAD thing; it can prevent formation of a film if clearances are too tight. It IS possible for some clearances to be too loose and for others to be too tight. So yes, it may leak slower, but that's not a nice tradeoff.

But as has been said before, the wrong oil is (usually) better than no oil. However, bad things may happen if you try to put gear oil in there.

Putting some conventional in there is very much like changing the oil with conventional, or with a synthetic blend. BFD.

 

[exbass94]

What about detergent oils? Are they compatible with non detergent oil?

Non-detergent would probably be compatible, but I sure as hell wouldn't put it in any modern engine. I honestly don't even really know why they sell that crap anymore. Mixing conventional and synthetic however, is perfectly fine. If you look on the back of any bottle of synthetic, it'll even say "compatible with conventional oils."

 

[Ranger Dave (B25)]

But as has been said before, the wrong oil is (usually) better than no oil. However, bad things may happen if you try to put gear oil in there.

I actually ran my 84 Ranger on half oil-half gear lube because the valve guides were so badly worn. Didn't do half bad, drove it for 50k miles before I gave it to my youngest, stupidest brother - who within 3000 miles blew it up treating it like a Mustang GT.

Never let him have - or drive - another one of my vehicles after that.

 

[OilPatch197]

I actually ran my 84 Ranger on half oil-half gear lube because the valve guides were so badly worn. Didn't do half bad, drove it for 50k miles before I gave it to my youngest, stupidest brother - who within 3000 miles blew it up treating it like a Mustang GT.

Never let him have - or drive - another one of my vehicles after that.

That would be like using that STP oil treatment stuff, thick as honey.

 

[LearjetMinako]

But as has been said before, the wrong oil is (usually) better than no oil. However, bad things may happen if you try to put gear oil in there.

Hmmm, gear oil! You know somebody has done it before.

As for semi-synthetic. According to Valoline, their blend is 1 part syn, 5 part conventional. Don't know about the rest, but its probably close to the same.