dont do it man, youre asking for trouble

 

We just picked up a 05 se v8 w/32k on the clock ~ about 3 weeks ago ~ driving around houston (traffic) we have been seeing a little over 14 with me driving and around 13 when she drives (we traded off a smaller very peppy suv and she hasn't gotten used to it yet) i have managed to get it to over 15 but i had to manually shift to get that ~ moving it to 6th much sooner then just driving it ~ we are currently vacationing at the outter banks in NC ~ which is about 1600 miles ~ here is the run down on speeds and mileage we observed on our trip out

tank 1 ~ 17.3 mpg @ avg speed of 62 (lot of traffic and construction)
tank2 ~ 17.9 mpg @ avg speed of 73 (open road lots on cops)
tank3 ~ 19.2 mpg @ avg speed of 71
tank4 ~ 16.8 mpg @ avg speed of 82 (no cops routinely over 95) ~ this is the most impressive number for a vehicle that large to get this type of mileage at these speeds is great to me
tank5 ~ 19.8 mpg @ avg speed of 58 (no speeding for me in NC since if you get busted anywhere in the state over 80 you physically must appear in court or have a lawyer (found out on vacation last year) we got great gas mileage but most of the driving was at 55)

just my thoughts figured i'd share

 

I assume you still have stock tires on it. Change them out for 265/60/18 Silent Armors and watch the milage go over 20 easily. The ratio of that size tire with the gears just seems to work much easier on the wallet and as I recently found out with mine, when you find the sweet spot for PSI on them (40 PSI all around for me) they roll so effortlessly on the highway, not to mention quiet and super comfortable. I recently took a new loaner LR3 for almost a week while mine was in the shop waiting for a Throtle body to arrive over the weekend and my wife turned to me and said that just then she realized just how much smoother my truck's ride was compared to a brand new LR3. The right tire makes all the difference!

 

I have the same tires and would love to get that milage (currently avg. 14 with the 91 octane). I know its early, but have you notice any potential for uneven tread wear with that little extra psi?

 

I made the change to 40psi very recently so if it was going to show signs of uneven wear, it would take a while longer. However, I am looking and will inform inmediately if it does. The front tires looked a little under-inflated at 36 where I had them before. Now they look just right at 40 so I don't forsee overinflation wear signs, but will post quickly if I do!

I'm fairly sure I lost just a hair of ride comfort with the extra 4 psi (either that orI have a very live imagination) but the extra gas milage I gained is noticeable as well and using less gas wins the battle right now!

 

2005 HSE

city 15-16
highway 18-20
91 octane

i do mostly city driving.

 

Yeah, I figured it was too soon to tell. But I'll keep an eye out for anything in the future.
I'm going to increase the psi and see if I can get improved results. If I encounter any issues I'll post as well.

Thanks for the info.

 

I am a new owner, but i've been averaging 15.4 on the city and 18.7 on the highway with stock tires and a light foot. does driving in the manual mode would help, as I heard somebody else comment on this.

 

Getting better tires would help a lot more .

 

I made a 320 mile trip yesterday, on 90% highway and I averaged 21.2 miles per gallon. But I don't know how accurate is the computer. But not bad at all with such a large car, with 300hp.I was driving at 75 MPH AVERAGE, with mid to low winds. when I turned the a/c off I was making 21.5 miles per gallon. Is this average or should i expect more?