I know its bad practice to mix synthetic with conventional oil. However, is it ok to interchange different brands of synthetic? For example, one oil change I may want to use Mobil-1, the next Penzoil platinum. Especially when I am on the road often and may be able to find only one, not another at any one instance.
Who told you this and where is the proof? Ever hear of a synthetic blend? The public has been duped into thinking that synthetic oil is the magic elixer and that conventional oil is worthless. In reality, synthetic oil MAY be better than conventional oil, but the in last 10 years conventional oil has made significant improvements. BTW, the "synthetic" term may be misleading. Conventional oil can be called synthetic if the refiner plays with the molecules a little bit. There are big differences in the way synthetic oil is manufactured. I wouldn't worry about using different brands of oil from one oil change to the next and I've got a 300K+ miled car to prove it.
Most oils-conventional and synthetic-meet SAE standards which state that they must be compatable and mix with any other SAE oil. They must mix both manufacture wise and viscosity wise. Most synthetic blends don't have much more than 10% synthetic in them, except Motorcraft (Ford), which has over 50%. Even Walmart's Super Tech oils get good reviews from Blackstone Labs and Bob the oil guy. They say that the Super Tech Full Synthetic, at $13.82 for 5 quarts, may be one of the real deals out there!
yeah, totally safe. try to remember your orig. viscosity and roughly match that. even if you can't, it's still better than running low oil levels.
Why? True, you don't get the whole extended life of the synthetic once you've mixed in conventional, but there's no harmful interaction. Synthetic oils specifically state that they mix with conventional oils just fine.
No harm whatsoever, provided both brands are equal in quality. Some might argue that alternating additive packages might provide some added margin of protection, but I doubt that.
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