Thanks rmoor for your feedback. Very intersting analysis

 

Today I drove my Tahoe in the city with temperatures in low 20s, what a different experience it was. As if I am driving another car. It goes to autostop much faster and stays for a *much longer period of time,even in slight uphill roads.
Although I didn't see a very noticeble differance in switching from v8 to v4. Or staying in v4 for longer period.
Other than it switches to v4 earlier in the drive than it does in colder weather, due to the trans temp being above 20 c at the start.
i am sure this will help my city mileage positively *but time will tell by how much.

I just thought to share my experience with you all

 

Just run at highway/autoroute speeds long enough to get everything good and warmed up, burn off cylinder deposits from unburnt fuel due to cold starts/short trips, etc.

 

Guss when I get over lets go for a long tour through the country and see if we can improve the milage, I buy gas and food.

 

is premium better in preventing deposits and having a cleaner engine or is it the easily burned regular?

 

...our cars are "tuned" to run on regular octane premium doesn't have much effect except to your wallet. FUEL ADDITIVES on the other hand make a great deal of difference. I ONLY use CHEVRON gas with TECHRON. I have used it for years in all my cars and have never had any fuelrelated issues, fuel injector problems or anything else like that. I believe texaco has techron as an additive as well.

 

Kc, thanks for your reply.

Ken, sure, no worries about the food and gas though

 

Chevron is one of the recommended Top Tier fuels, a fuel quality standard endorsed by GM and several other major OEMs.

http://www.toptiergas.com/

Ford and BP have their own standard, so that's why neither one of them are part of the Top Tier program. But I would trust BP gas as well.

 

KC135R what do you think about fuel additives? Also I have been in the Aviation fueling business for a few years and transportation, care, and Maintenace of the fuel is also important. I have seen large tanker trucks down loading there products in pouring rain. No question even with filters, clear and bright testing the product is degraded. Also fuel starts to lose its octane rating from the day it is made, not sure about additives there are so many. Also I agree with Jet 1 that priemum fuel is a waste of money, however is not the refining process for higher octane fuel better. Also I believe that in the colder climates the fuel manufacuters add an additive during the refining process in the winter months.

 

when you say tuned is it "tuned" to accept a lower rating but it doesn't mean you cannot put a higher octane. as specified, the 6.0L can run on 87 "or higher." it doesn't say 87 only. I accepted the notion of filling with regular(shell) in this cold weather and the best I got in "auto" mode was 17.7 mpg(city/highway). before changing to regular, I have been using premium(shell) and would consistently get 20.4 mpg city and 20.9 highway also in "auto" mode. doing the math, mpg vs cost, the difference would only be 20 cents more of the premium PER 26 gallons(assuming the premium is 20 cents per gallon more expensive). to achieve the same mileage would require 2 more gallons of regular vs premium.