Mixing grades/brands and varnish

[VeeDubb]

I dug up an old link about varnish:
http://www.bobistheoilguy.com/forums/ubb...true#Post964071

It appears that there might be some tentative though inconclusive evidence that mixing brands and additive clash may produce varnish. So I have tried to use the same brand as much as possible.

My question is: might there be a risk of additive clash when we are switching grades within the same brand? For example, many of us are fairly confident that M1 0w-40 is a different beast from the other M1 formulations. So if one were to run M1 0w-40 in the summer and 5w30 in the winter, will that produce similar additive clash as switching brands? I'm thinking about running synpower 5w30 in the summer in the Toyota and then 5w-20 in the winter. I am wondering if this a bad strategy relative to just sticking with one grade year around?

 

[buster]

I have often wondered the same thing, however most people change brands and never have this problem. I think switching back and forth won't cause any problems at all.

 

[mitchcoyote]

There is no need to switch to 5w-20 in the winter, you can stay with the 5w30 year round.

 

[Drivebelt]

JAG's second to last post in that thread addresses the issue (relating to old Group I turbine oils being mixed with Group II's which didn't have the solvency to keep all the broken down garbage in Group I oils in suspension).

One of my old (SH) bottles of Syntec says on the back … "Castrol Syntec is compatible with all conventional and synthetic oils".

 

[AEHaas]

It seems that there would be rare instances where there might be a clash. To be completely safe you should consider always using the same oil. There is no need to use the 30 grade during the summer. I would be comfortable using the 20 grade all year.

I just changed the Enzo oil from Castrol Syntec European 0w30 to Renewable Lubricants Incorporated 0W-30, a vegetable based oil. I drained the oil, filled with the RLI then ran the engine up to temperature. I then changed the oil again, right then. Since I was going to a completely different oil I wanted to be sure the old oil was all out of there.

aehaas

 

[VeeDubb]

AEHaas,
Would you do the same flush if you were changing grades within the same brand?

 

[AEHaas]

If I was changing only a single grade then I would not do a flush. If I was increasing or decreasing 2 grades then yes, I would do the flush.

When I originally went from the Shell Helix Ultra 10W-60 to the 0w30 Castrol I did the flush for both a viscosity and a brand change.

aehaas

 

[VeeDubb]

Thanks. That's helpful guidance.

 

[yannis]

Link to John Rowland's thread.
.
.
.
15) If you need to top up your engine oil, how important is it to use exactly the same brand and type?

Not very important at all. Unfortunately, due to ‘arse covering’ reasons we cannot print this advice on the can! Although officially all manufacturers advise against mixing different makes and grades, in fact there is very little chance of any harm being done, even if one is a mineral 20W/50 and the other is a 5w30 synthetic. Obviously, avoid this if you can, but do not panic if there’s no other alternative. Just don’t mix 2 stroke and 4-stroke oil!

 

[pbm]

Would there be any harm in mixing a quart or two of Mobil 1 0W20 with Mobil 1 5w20? Sometimes Walmart doesn't have enough of either weight for a complete change. All the rumors of the 5w20 being Gr.3 while the 0w20 is still Gr.4 have made me wonder.

 

[JohnBrowning]

No problem at all.

 

[Audi Junkie]

Before coming to BitOG, I'd usually mix 5w30 and 10w-40 to get a visc that "felt" right in my Euro cars. Now I try to stick with just one grade, but sometimes end up mixing 5w-20 and 5w30 weights.

 

[bmwtechguy]

I want that flush oil, AEHAAS! Seriously, what do you do with it? Dispose or recycle with oil that has actually been run for a complete interval?

 

[byez]

Seems like a waste of oil for "most" of the cars here although I would do the same if owned an exotic car.

 

[Audi Junkie]

Even in an exotic, I'd use that oil for topping-off. Dr.Hass' cars look like a bunch of oil burners anyway. ;o)

Honestly, I plead guilty to re-using oil. Not so much in my main vehicles, but topping off other people's and garden equip. The use varies with condition. Last winter I dumped some Mobil 1 after like 1k because it was a blend of different grades I decided against. It was used ALL winter in my needy friend's old Audi. Yesterday, I just brought home a used mower with black oil. I ran two 5 min ocis of old disposable-grade car oil before changing it to new.

What was this thread about anyway?

 

[mechtech2]

Umpteen jillion people have mixed engine oils with no problems.
I favor using the same sauce, if possible.
I can't think of a real problem attributed to oil mixing.

Varnish is usually from excessive heat, poor PCV systems, or overdue oil changes.

 

[BrianWC]

Originally Posted By: mechtech2
Umpteen jillion people have mixed engine oils with no problems.
I favor using the same sauce, if possible.
I can't think of a real problem attributed to oil mixing.

Varnish is usually from excessive heat, poor PCV systems, or overdue oil changes.


I am all over the map in my brand usage but my main mix I come back to is 2 qts of M1 10W30 plus 2 qts of M1 15W50 with a bottle of SLOB. For the Honda, I'm even more casual, throwing in pretty much anything that doesn't contain pea gravel.

There was a link that JAG or someone posted a year back about mixing various group III's yielded unexpectedly short service life with some mixes. Never saw anything directly discussing varnish, though.