Synthetic or Conventional Oil?

[baskerj]

Mobil1 is a pure synth oil:

http://www.mobiloil.com/USA-English/...AQs.aspx#FAQs3

A great site for oil research is:

http://www.bobistheoilguy.com

Check out some of their forums.

[LTZ2FLIP4]

Every vehicle Ive ever owned, Ive changed the oil every 2000 miles. Used conventional oil. Personally I think all this synthetic crap is just to empty your wallet faster. The dumbest thing Ive seen recently is that Mobil 1 5000,7500, and 15000 mileage oil. Are people that focking lazy that they cant change oil every 3000 miles?

While we're on the subject of oil, I would just like to thank the designers at GM for designing another shitty drainplug/filter location on the Trailblazer. I changed my oil for the first time since buying the TB about 2 months ago. What a PITA to get at the filter. And why have a cover to get at the drain plug?

[Mr. Northface]

Why are somepeople using the TB's computer to tell them when to change the oil? Isn't that bad?! I don't see why it is so hard to get it done every 3K.

Is it really that bad to wait longer than 3 months to change it though?
It is going on 4 months & I still haven't had it changed. Not there yet with the 3K miles.....but I don't know if I should press it..............I will get it done sometime this week just to play it safe.

[lkurek]

Sigh.....

OK, for you guys that continue to use dino oil, or insist on changing it every 2000 (!) -3000 miles...power to you. It's your car/truck.

However, it has been documented all over the net, and I personally have done oil analysis on my Z28, and have verified that the additive package in the synthetics (Mobil1 in my case) don't start to fall off until well over 12K miles. From a pure engineering and chemical basis, there is NO REASON to change your oil before then. NONE. The oil change monitor on the truck is used to calculate oil change intervals based on driving habits and conditions. The old 3000 mile rule was good for the most extreme circumstances, and still left you a margin of error. Read your manual, and you will see that even without the monitor, suggested oil changes under normal conditions is WELL over 3000....

I do have to qualify this and say this is true only for late model fuel injected motors. If you have an old school carb'd motor, then I would say test the oil, or stick to the 3K rule. With the precision fuel metering of fuel injection, there is little if any wash down or dilution of the oil...from either raw fuel, or combustion byproducts. Carbs are different.....

Bottom line:

Synthetics are MUCH superior to dino oil

As long as the chemical nature of the oil is within spec, there is no reason to change it early.

[balboasdelight]

Originally Posted by lkurek

I personally ... have done oil analysis on my Z28, and have verified that the additive package in the synthetics (Mobil1 in my case) don't start to fall off until well over 12K miles. From a pure engineering and chemical basis, there is NO REASON to change your oil before then. NONE.

Perhaps... but there is a reason to change the filter before then.

I agree 2K is silly, but IMHO 12K is stretching it. 6-8K works for me (synthetic), swapping a new filter at half that. Probably more important than the oil change frequency is religiously checking the oil level, and monitoring the pressure. And avoid the gimicks, like Slick 50.

[lkurek]

As for changing the filter more often....

The only reason to change the filter, is that it's efficiency gets reduced due to buildup of crap. Most of this crap is sludge or other carbon deposits, which are normally formed by overheated/broken down oil. As the synthetic doesn't break down like conventional, nor does it form sludge....the filters could, in all honesty, probably last the lifetime of the vehicle. The biggest breakdown factors while using synthetic is contamination due to blow by, condensation from the normal heat up, cool down cycle, and particulates passed through from bad air filters...

[balboasdelight]

Originally Posted by lkurek

The only reason to change the filter, is that it's efficiency gets reduced due to buildup of crap. Most of this crap is sludge or other carbon deposits...

And wear metal from the engine (rings, bearings, etc.), which is largely independent of oil age, assuming the oil is still within its useful lubrication life. Granted, it is more of a concern at break-in than later in the engine's life. A magnetic oil plug will attract metal filings, as an indicator of their relative accumulation. Sure beats cutting open a used filter.