mixing oils

Sure.

You won't get much of the benefit from the synth, but it won't HURT anything.

--- Rich

bobby F wrote: Is it safe to mix synthetic and normal oil together?

Of course. Blends are commonly sold, though the only benefit to mixing them is increasing your cost.

An older engine might experience leaks from the seals and pan gaskets when switching TO synthetic, and may consume a bit more oil. In that situation, you're actually better off, in dollars, changing your dino oil more frequently, and ignoring synthetic. If you have a newer engine, want to increase your oil change interval, and if you live in an area where the ambient air temps stay below freezing for extended periods of time, those are good reasons to use synthetics. Otherwise, stick with plain dino and an oil change interval of 7500 miles or less.

good luck! GTr

Not a problem, but why mix? I use a name brand 5-20. My son buys cases when they are on sale. He buys filters on sale. And modern engines do not dirty oil much in 3000 miles. Perfect for older trucks and tractors for those that truely believe in recycling.

mixing is a waste. But going one way or another isn't. The virtues of synthetic oil is well known. I'm using 5W30 Mobile 1 in my 10,000 2003 Tacoma with change intervals of 5000 miles. Using dino 20W50 in my old '85 2wd truck, 4,000 intervals since new.

Just had an oil change at 10,000 > Not a problem, but why mix? I use a name brand 5-20. My son buys cases

Safe but maybe not the best protection. Each type of oil, even the same brand, has an additive package specific to that oil. Mixing the additive packages might not give protection equal to either of the individual oils. A commercial blend has a single add pack suitable for that product. But, I find commercial synthetic blends not worth their price.

Either stick with a good conventional oil with 5k oil changes or a top quality synthetic for 7500 or 10k oil changes.

Ken

The only caveat would be an engine flush every couple years or so using dino oils. The sludges in the oil pan can get pretty thick and the complex mix down, and there's a bunch of constituents that do form, may cause problems if it's drawn up, then again, maybe not.

Tacoma Dude, just to add to your post for everyone's elucidation, the reason why conventional motor oils darken up is mostly from oxidation from the high heat in the top end, followed by the complex of organic reactions occurring from the sheared alkanes reforming into different compounds with differing refractory properties. There's also the effects of water and acids interacting with the oil, creating permanent and transitory products, some with poor lubricating and/or heat transfer properties.

Here's a real fun experiment: gather together a fry pan, a high temperature thermometer, and take out to the barbeque. Keep a dry chemical extinguisher handy. In the pan add a cup or so of conventional oil. To make it really fun, use Castrol racing oil. Heat the oil and check the temperature of the oil making sure to keep it under 350 F and let if cook for 10 minutes or so. Pull it off and let it cool. Voila. Black oil. It's oxidized, or in other words, burnt.

Do the same for some synthetic oil, and let it cook away for a while. The color will be nearly the same as when started.

Interesting thing about oil formation: oil cannot exist as a crude in temperatures of over 200C. In fact, temperature and duration of the "cook" has a lot to do with whether the oil is paraffin based or asphalted.