thdrill

Hey all, I am new to the forum with my purchase of a 2003 used Tahoe with 43400 miles on it. I has the V8 5.3L engine, and so far am loving it. Now,(with the exception of selling it (yeah right)) I am looking to do the most with the MPG as possible. Right now it seems to be averaging between 12 and 14 mpg, but as always more would be better! I have seen posted here multiple times that people have gone to synthetic oil and have noticed an increase in mpg of 1-2 mpg. However, in looking into synthetic I noted that the oil change at a "Jiffy Lube" kinda place is exuberantly more for synthetic over traditional, and to do it at home is almost two times the cost. The question I have is do you recoup the extra money in the mpg or is it really a wash?

GIXXER

synthetic oil will do nothing in way of adding fuel efficiency. The benefits will be potentially extended drain intervals (verified through used oil analysis), better cold weather start-up and all around better engine performance.
A true synthetic oil is comprised of 100% man made PAO's (polyalphaolaphins) which are perfectly round and totally uniform. This is considered a high end, or base 4 oil. Non true synthetics are also graded on bases, 1 being lowest and 3 the highest, and are attempted to be forced into becoming perfectly round by way of chemical processing and treatment. What and how does this affect the engine? Think of a pillow case full of rocks...now try to squish them around. There isa lot of resistence. Now think of the same pillow case full of marbles...now squish them around. It would be much easier as each marble is perfectly uniform with no jagged edges to add resistance and friction. This is the same thing with oils. All in all there will be no value added by way of increased mileage. Also, measuing such is impossible as there are too many variables to hold constant. I.e. one day maybe headwind, or didn't drive as aggressive, etc. Benefit comes by decreased wear in the engine.

ZX1100F1

I'm not going to get into the shape or molecular structure and composition of synthetic motor oils since I am not a lubrication engineer but I will say that in tests on the current GM 5.3L engines that Mobil-1 5W-30 has been tested and compared to conventional 5W-30 motor oils and it was found that it is superior in virtually every accord.
Horsepower, torque and fuel efficiency were up when synthetic oils were in the oil pan, it is no secret that synthetic oil offer superior lubrication properties vs. conventional motor oils but you’re question is “is it worth the extra cost?”
The answer is “It all depends”. Even though the motor may get slightly better fuel economy the reality is that it is not going to be an improvement that you notice (maybe + .5 mpg is all) and it certainly will not offset the additional cost of the synthetic oil change.
There is also the issue of reduced engine wear associated with synthetic oils use, I don’t think that anyone will argue this point but is it worth the extra cost?
Probably not, unless you plan on driving your Tahoe until the wheels fall off and even then the extra expense of all the synthetic oil changes may have added up to the cost of an engine over-haul by that time but the stark reality is that 95% of the customers that purchase a new vehicle do not keep it and drive it beyond about the 5 year mark, with 70% not keeping the vehicle beyond 3 years 2 months.
If you want the peace of mind of knowing that you have the best possible product in your crankcase then use a full synthetic motor oil otherwise you’re going to have to make the call.

Do you drink tap water or bottled water?