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I heard that different brands of oil will not "mix well" sometimes and can cause sudden oil burning. I just bought a used truck and don't know what brand of oil was used the last time it was changed. There's a good chance the dealer did it last, but I'm not sure. If it gets a little low, should I just change it all to make sure I don't have problems rather than add some not knowing what brand was used last? Or, does it just not matter at all?
</font><blockquote><font class="small">In reply to:</font><hr />
heard that different brands of oil will not "mix well"
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Danny, I think that was certainly the concensus of opinion 40-45 years ago. They supposedly used different additives and detergents and it was commonly believed that mixing them or changing brands would cause a vehicle to "use" oil. Now I don't know whether that was a fact or not either then or now, but I don't think it's generally believed that much anymore. If you use an oil with the same API and SAE ratings, at least theoretically there should be no problem, they should be compatible. Now I'm one of those who would still much rather pick one brand and stay with it, and the first time you change oil, that's what I'd do; however, if you need to add any before then, if it were mine I'd just add whatever I planned to use in the future and not worry about it.
Personal opinion, no scientific knowledge. [img]/forums/images/icons/tongue.gif[/img]
I agree with Bird's answer on this issue.
Danny,
As a rule of thumb, I change all fluids right after purchase of any used vehicle. [img]/forums/images/icons/wink.gif[/img] It's kinda cheap insurance and lets me know how all those fluids look, and know when the next change out should be, so I can start my own maintenance schedule.
Steve
My money's with Steve - just change the oil. May be unncessary but how many people will bother changing the oil knowing they're going to be selling the car soon? Much more likley that it's due anyway and by changing it now you have a place to start and can deal with a known quantity.
>> how many people will bother changing the oil knowing they're going to be selling the car soon?
Lots of them. When you sell a car you want the oil and other fluids to look good. If they look like junk a lot of people won't consider the truck.
Don't worry about adding a quart of oil of your favorite brand to bring the level up between changes - it's not a big deal. Just use a good quality oil of the recommended viscosity.
<font color="blue"> Lots of them. When you sell a car you want the oil and other fluids to look good. If they look like junk a lot of people won't consider the truck.
</font color> How exactly do you tell if oil needs changing by looking at a dipstick? I'm not talking about oil that's been in a vehicle for three years and looks like tar. But I don't think you can tell the shape the fluids in by looking at it. Most oil after a month or so is going to look black. Synthetics will be very black after 6 months and may still be very serviceable. If someone was conscientious enough to change the fluids when selling a car they would also likley have records to that effect. Absent that I'd change the oil.
I agree too. I know that' comforting [img]/forums/images/icons/wink.gif[/img]
An oil change is cheap. After buying a used vehicle, I'd change oil and filters(air and fuel). It's cheap insurance, and then you know what you've got too. If it has any kind of miles, I'd at least inspcet rotor/cap/plugs/wires too. While you're in there, check the tranny and differential fluids, power sterring, brake fluid ect too.