Red08

I'm sure the answer is NO, but you never know what can be learned on the forum. I have a quart of regular Mobil 1 oil from when I had the oil pan gasket replaced. When I change the oil again, I will use Mobil 1 EP. I will add 5 qts of the EP and .5 qts of the regular Mobil 1. I ask my CF bretheren...any problem with doing this?

FlyerVette

Waiting to hear the answer on this too. Off the cuff I can't imagine it being a problem.....but as you would like confirmation of this.

Rich Mickol

I'm waiting too but like my friend above, I think you'll be fine.

Hey George, hope all is well. Florida has arrived in NJ.

LMB-C6

Same viscosity and both meet dexos 1 spec? No problem. I would use the full quart of regular M1 and top off with EP just to use it up.

biker1059

why waste oil, I do that all the time with no ill affects, but I never mix more than a quart of something else. Im talking about brands or types not weights.

AORoads

I'd like to hear from the former oil engineer LDB. But I'm like the rest: I doubt it will have any negative effect. I could be wrong, but I doubt also that Mobil 1 full syn. was changed or reformulated to also meet Dexos standards; it just does as it is and was formulated. So, no conflict there imo.

As to Mobil 1 being fully compatible with Mobil 1 EP, that is the issue. There being a probable high number who might switch from M1 to M1EP, with a residue of M1 left in the engine and crankcase, I can't imagine that one would react badly with the other. Or, there'd be instructions not to use it after the other's been used on the bottle.

I could be wrong, but I think I recall seeing warnings on the bottles of antifreeze (admittedly, quite a bit different from M1 and M1EP) not to use "green" stuff after using the "orange" stuff.

TerryL

You were right, NO is the answer.

CorvetteSparky

This information is on the Mobil 1 site:

Mobil 1™ synthetic oil is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. However, it is important to note that the superior performance of Mobil 1 oil will be reduced by diluting it in any way.

However since you're mixing 2 Mobil synthetic oils I wouldn't expect much reduction in performance although apparently the EP is better in some way. I believe the sentence above is talking about mixing with conventional oil.

SlayerRX8

Same brand, same weight, I wouldn't be worried.

Some brands vary a bit by weight, but they're both Mobil.

LDB

Gosh, I’m flattered to be asked in advance. You’re right, oils and additives are supposed to be tested for compatibility with standard oils, so theoretically, they should all mix ok, and most do. I can’t imagine that two similar oils from the same company would fail to mix ok. The few cases I’ve seen where there were problems were from oils from different companies, that were also very different in character (such as one specifically aimed at full racing with one specifically aimed at very high mileage cars). It’s not so much the base oil. You can normally mix even dino oil with the various classes of synthetics. If you’re going to get into a problem, it’s normally with the additive packages, or especially with aftermarket additives. So bottom line, if you stay with the same company, they probably use the same families of additives (just in different proportions in the different grades), so you should be fine. Even if you go with different companies, or mix synthetics and dino oil, risk is still very low. But at some point, if you mix different companies, and different base oil classes, and different applications (like racing versus high mileage), and especially if you add aftermarket additives, risk starts getting nontrivial.

AORoads

Thanks, LDB! Helpful, as usual.

FortMorganAl

This year when I did my oil change I bought the usual 5 quart jug of Mobil 1 and put that in first. When I went to top off out of a second several year old 5 quart jug of Mobil 1 the color was noticeably lighter. I immediately checked the jugs and the labeling was identical. Evidently Mobil has changed formulation in the past few years but didn't consider it significant enough to even add "NEW AND IMPROVED!" to the label. Surely additives don't settle out in oil sitting on the shelf.

ZR1 136

Thanks for asking the question. I have Mobil 1 EP and a quart of Mobil 1 from the Corvette corral hand outs at Sebring. I only use Mobil 1 in my Corvette and my Ford truck. Scooter gets regular Harley oil.

R&L's C6

I'm pretty sure it wouldn't make any difference, but for the $5 bucks you will be saving, why chance it?

Just bite the bullet and buy that extra quart....

carpe dm

Done that.... no problem here.

Richard Ames

There is still some oil left in the engine when you drain the oil. If you change the type and brand of oil you are "mixing oils" a bit any way. If the oil meets specifications it is fine.

SCcues

RnLi

Been mixing Mobil 1 oils, in varying combinations for years......sometimes in the exact proportions you question. Haven't had ANY engine problems in any of the vehicles (omitting the infamous DexCool problem, which is unrelated).

The past year, have been using JUST the Mobil 1 EP. Not happy with results. Going back to the regular product.

Your choice, but IMO, will not cause any problems.

Skiman

Could you elaborate?

zero11

No problem,oils are same company Mobil I.