After each engine oil change, small amount of oil is left. Can these be put together and used for next oil change?

They are of different brands, and different weights: Amsoil 10W-40, Amsoil 20W-50, Castrol Syntec 5W-50, Shell Rotella T 15W-40, Mobil 0W-40, etc.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

Why not just use the non-synthetics for fuel?

It'll burn.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Can you do that without filtering it? Why can't synthetics burn too?

Edit: Oh you meant the unused oil, right? Why would anyone have several different grades of oil at the same time anyways?

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
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04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

I guess your diesel does not use any oil. Generally I find any leftover oil goes into topping the oil level periodically before the next oil change. I don't know of any readily available motor oils that can't be mixed together. I find that Rotella Syn. 5W-40 works well all season so I never have any stray bottles laying around.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Mixing that many oils together probably isn't a good idea. Different oils weights do not mix.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

no, they can't. Get an old pickup truck and use it in there.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I was taught you can mix viscosities but you don't know what would happen if you mix manufacturers.

What are you talking about?? If that was the case there would be huge warning labels on oil bottles warning you not to mix them. There is no way the oil is not going to mix together just fine. How many cars do you see blowing up because of "incompatible oils"....

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Read the many oil threads on this forum. Two quarts of 10w-40 and two quarts of 15w-50 do not equal four quarts of 12.5w-45. They equal and behave like two quarts of each weight in the engine. Weights don't mix, you can mix brands no problem though. Ie two quarts of Delo 400 15w-40 will mix just fine with two quarts of Delvac 1300 15w-40.

I wouldn't put that cocktail into an expensive MB diesel. Dump a quart in each tank and stop buying so many different types of oil! You only need one all year.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

An unimpeachable source!!! Anyway throwing a quart of whatever into your motor is not going to send it to the scrap heap. But I agree in sticking to one oil rather than buying the $0.99 special of the day at the local McParts.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

I have been told by a very good mechanic that mixing weights of oil is a bad idea, different brands, same weights OK

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Ron
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How about the dangers of mixing the different types of detergents present in the oil as well?

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Think Alternative Energy!
300CD '80 (now gone but not forgotten...)

Looks like your best alternative is to use it as fuel.

As far as the synth stuff, I thought I read something that has a negative connotation attached to burning it as fuel. Maybe deposits or burning qualities, or build up of some sort - I really don't remember.

If you decide not to use the various old oils as fuel, then bring it to a parts store or any other place that accepts used motor oil.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

You hit the nail on the head. Different viscosities don't amount to crap, it is the additive packages that could cause a problem. Even that is a very rare occurance any more, but still the possibility does exist. If I have odds and ends of oil I use them up in the lawn mower when I change the oil on it.

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Keep everything as simple as possible-but no simpler--Albert Einstein

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)