9550

im stupid so i bought the wrong oil today. bought a 5.1 quart jug of 5w-30, needed 5w-20
i didnt realize it until i filled my filter and poured about .5 quarts into the engine.
luckily i had enough single quarts of 5w-20 and remains of previous 5.1 quart jugs to finish the job.
so, how bad is it that i mixed the weights?
i suspect not bad at all , but what the hell, i might as well ask.
thanks

bluebeastsrt

You'll be fine. Dont worry about it. It's the same weight oil.

craig71springsport

Nothing wrong with that. If you're more adept to beating your ride, a slightly thicker oil will do you good. Get some of that LucasOil stabilizer too, that stuff is awesome.

Before I pulled the engine out of my 71, I would put 20w50 in it to try to make the valve tap it had less annoying, worked too!

Old Mustanger

Different brands of oil do NOT mix well, even different weights of the same brand do not always mix well. They have unwanted and sometimes very bad chemical reactions. There are differences in base crude and huge differences in detergents and chemical additives. These chemical reactions are what cause the gunk and crud buildup in your engine. The sand-like crystals that you find in your engine are caused by heat & chemical reactions due to incompatible oil compounds.

If you want your engine to have the best chance at a long life, choose a quality brand and weight of oil to start with & always use the same, never mix oils. Even when you change the oil there is 10+ oz of old oil left in the valleys & oil galleys, so you never change "all" the oil. That is why it is important.

I've torn into engines with only 35k miles on them that had an inch of crud buildup already. The owners always purchased the cheapest oil on sale & changed brands on every oil change.

I changed valve cover gaskets on one of my engines with 200k miles on it and it was just as clean as new with no gunk, so it does make a significant difference.

Pick a good oil to start and stick with it, that will give your engine the best chance at a long life.

9550

are there any oil additives that can clean up this crud buildupthat may or may not be there already?

Derf00

As long as the API rating of the oil is the same (Not SAE weight class), it is highly unlikely to cause any problems if its between brands. If it's the same brand it's even less likely. API ratings are there to inform you of the basic additive (chemical) package that is present in the oil you purchased.

The difference between brand X vs brand Y, as long as the API is the same and the type of base (dino oil, synth-blend, full synth etc) , are additional "magic" additives the oil mfg has added to set their product apart from others (marketing).

http://www.api.org/oil-and-natural-g...10_120210.ashx

A slight ooops of adding 1/2 quart (even a quart of two) of 5w-30 to 5w-20 or vice versa is not going to hurt anything.

Old Mustanger

There are additives available, but the dissolved goop has to go through your oil pump before being trapped in your oil filter.
A certain percentage of the goop will be in a crystalline form. I am not positive, but I would guess that some of the crystals will also travel through your oil pump, that can't be good.
If you have a goopy engine, the best solution is what bluebeast did, remove the valve covers, valley cover/intake and the oil pan so you can scrape & clean everything well. Then throw in a new oil pump.
After that, don't mix oils and the goop will not come back.

I have seen a few engines blow from running cleaning chemicals through them. A couple were because of chunks of goo clogging up the oil pickup, and a couple were caused by oil pump failures.
You could try it, just be prepared in case something really bad happens....

Old Mustanger

Maybe, maybe not.

Probably true for a one time occurrence. The REAL problem is when it is done habitually.

The API is a performance standard, not an ingredients standard. It specifies the performances like viscosity at certain temps, film strength, etc.
Although they make a simplistic statement in the sidebar that oils that having the same API standard should be compatible, my experience would be otherwise.

Earlier in my career as a contract Engineer I worked for a company called Morbark in Winn Michigan. I worked with a chemical Engineer charged for discovering why Deutz diesels used in some equipment were blowing up in the western states, it was costing the company a lot of money. The engines were not blowing up in the eastern states or Canada, only in the Western states.
The cause of the blowups was the commercial oil we used sold by Sears at the time.
The Sears oil sold in the Eastern states was produced by a different supplier than the sears oil sold in the Western states, but to the same specs. The oils had incompatible chemistry. We shipped the engines with the east coast oil installed, but when the engines used oil in the field, the customers were using the west coast product to top off the engines.
The 2 oils when combined and heated produced a form of sulfuric acid. This acid ate the seals out of the engines and they were blowing up consistently.

The Engineer did compatibility testing on many easily available oils, looking for a more compatible solution and found issues in most combinations. Some created goo, some created acids and some crystalline structures that could be considered abrasive to engine internals.

So, for arguments sake, assuming I am full of crap, where do you think the goop and crystals come from?
I have torn down engines with over 200k miles on them that were totally clean as new.
I have also torn into engines with 35k miles that had 1/2" of goop everywhere.
I am curious as to how you would explain this?