quote:I recently put Delvac Super 1300 15W-40 in my LT4 Corvette with 45,000 miles on it. Engine runs great and doesn't burn oil between changes. The dipstick level didn't change noticably in 6,000 miles on M1 5W-30. It appeared to drop less than 1/10 of the way to the add mark. The 15W-40 is in there for a rinse cycle on ARx. With 15W-40 it seems to be a bit quieter and smoother. Because of new oil, placebo effect or higher viscosity??? Can't be sure which. Oil temp with M1 5W-30 cruising at 70mph on the freeway on a warm day ran 10 to 15 degrees above coolant temp on the digital readout. With 15W-40 it runs 8 to 14 degrees above coolant temp. The difference is well within the range of experimantal error for my crude measurements. I expect the 15W-40 actually runs a tad warmer but not enough to measure outside a dyno facility. In two days we take off on a 1500 mile trip, that will give me a chance to check mileage. This is my first summer with the car. If the oil temp doesn't go over 250F very often, I will switch to 10W-30 M1, if it does get hotter, 5W-40 SUV M1.
Originally posted by cheeks: I currently run Delo 10w30 in my '99 Suburban 5.7L. I am tempted to run 15W40 in it because it's relatively cheap and easy to buy a case at Sam's instead of ordering the 10w30 through the local Chevron jobber.
quote:I've said before as far as MPG goes, I believe this sealing effect cancels out the added drag of the thicker oil. The trick is to find the balance that works best for you. Newer car means less need for the sealing, so lighter lube works well. [ July 20, 2004, 11:17 PM: Message edited by: Audi Junkie ]
I consistently get a little better mileage with 15w 40 Delo. I suspect because of better ring seal