Estimating MPG with 33" Tires

I live in a hilly location, drive mostly city, and have to deal with California gas (which is basically water that smells like gasoline). For this reason, I average 13MPG (12MPG if I occasionally rev over 3K during my tank of gas, errr water). This on a completely stock, 6-Speed, V6, 4x4 truck.

Anyway, like many of us, I want to lift and I want bigger tires. I want to lift only 2" and run lightweight wheels (22 lbs each) but with Nitto Trail Grappler LT285/65 R18. Which are essentially 32.8"

So the question is... If I'm average 13MPG now, how much can I expect to average with the new setup?

 

13mpg? Somethings wrong here. On my 35's I was getting 21mpg on highway, 17 in city. I just changed to 33's about 100 miles ago, so I haven't yet calculated gas mileage, but im hoping to be getting better results.

 

Nah, Nothing's wrong. Every single car I've had here in SoCal has given me way lower MPG numbers than the sticker claims. Usually around 4 MPG less than the manufacturer's claim for city MPG.

It's the combination of hills and weak gas here. The hills here are pretty brutal on MPG.

 

Im also in CA. I have about 600 pounds of armor on my truck. Im running 265/70/17s with a 3 inch lift and I get an avg of 18.5 mpg

 

check your right foot, might be a bit heavy...also, if you get an Ultra Gauge you will real time feedback on the right foot...it helped my MPG, makes you really think about quick starts, WOT to pass, stuff like that...


you may think you are taking it easy, but, in reality, you aren't...


I can squeeze as much as 23MPG on freeway with careful big rig following at a safe distance, get an average of about 20MPG general stop and go driving, this is with a v6 auto in the hills of Southwest Virginia...

 

Hmmm. Not sure what the deal is then. Maybe it's a San Diego thing. I don't know. I've purposely driven in "fuel economy mode" plenty of times in various cars I've owned in order to calculate fuel mileage... and it's been consistently the same results. All cars I've owned, and the ones my wife has owned, have consistently yielded less than claimed by the manufacturer. In fact, in the MX-5 I just sold a month ago, I tracked every single tank of fuel since new. I was always at 21MPG give or take. That's a car that usually averages 25MPG.

I'm also very confident in my way of calculating fuel consumption. I even wrote an article with instructions on how to do it. This: http://rallyways.com/1448/how-to-calculate-mpg-by-miles-per-gallon-pumped/

Plus, the rare times I did only freeway driving, the mileage was much better. I even got 32MPG out of that MX-5 during one trip. On freeway only I manage 18-19 MPG in the truck once. I tell you, it's the damn hills where I live. City for me is 13MPG

 

21 MPG, 18.5 MPG, I'd double check those calculations.

 

The only other way I can double-check is using GPS. The math is spot-on. The only thing that could be wrong is the odometer in the truck. And it's stock.

I fill the tank. Zero out my trip odometer. Burn through the whole tank. Refill. Do the math according to how much I put in, which is how much I burned. Done deal.

I have a friend that has a 2007 with a 6" Procomp lift, a 33" Toyos. He gets 12MPG here in San Diego. And I don't even know what method he uses to calculate.

Then I know another guy that drives a 8" (?) lifted Gen 2 Frontier, Automatic. Heavily modded. He averages 9MPG around here.

My old 2011 Mustang V6. Ford claimed 22-31MPG. I always got 15 in the city. But, I took it on a long freeway trip and yes, it got me 30MPG.

It's the geography, topography, or whatever the heck it's called. Comes with living here.

 

california gas: check.

california hills: check.

california TRAFFIC: check.

california driving style: check.

Now, assuming you're already calculating correctly, and assuming that after you put on larger tires, you always calculate applying the correction factor for the speedometer and odometer difference induced by the non-stock tires...

Here's the thing, traffic and driving style with lots of acceleration is affected by a heavier tire/wheel (rotating mass takes more effort to accelerate) and your gearing gets a disadvantage when you up the tire size.

I bet if you're already getting a consistent 13 - you'll drop to 11.

One thing - on the hills - your propensity to keep the rpms low may actually be hurting you. If you find you're really having to put your foot into the gas to keep speed up while climbing in the gear you're in, try dropping a gear (or even two.) The better torque multiplier of the lower gear, combined with moving the engine further up its power band, may actually allow it to use *less* gas to keep you moving at the same speed. An automatic would NOT stay locked in top gear in these situations - it would automatically downshift from 5th to 4th, or even to third.

 

this on 31's i was getting around 16-17 theres no way someone with 35's is getting better mpg than me

 

Thanks for the advice on the RPMs, I'll try it. I usually aim to be between 2,000-2,500 in the hills. But I'll try at 3K (loud in this truck compared to my smooth Miata engines) and see what happens.

11MPG with the bigger tires sounds about right.

 

32" inch tires here with a 2.5" lift.

avg 15-18mpg.

 

Man, is gas bad in cali? I live in eastern NC and usually run 89. I have a v6 with 6spd and 285/70/17 which is basically a 33 and get about 16-17 mpg. Granted, i don't have many hills, but im not easy on the gas all the time. My shift points are usually in the 2700-3000 range.

 

There is nothing wrong with California gas, soon the whole country will be running California formula gas...


The only difference is the tighter smog requirements, meaning the additives in California gas are a bit different, the basic refined product is the same before the additives, it is not water, LOL

 

I get an average of 15 mpg with my 285/65-18's. . . Normal driving and I trry to keep it below 2k RPM most of the time.

 

Is it just me.... I don't even count it and just add gas when its needed.

 

^I track my gas milage only as a means to detect malfunctions in the truck.

The heavier LT tire will cause you to lose about 1 mpg, so from 13 mpg to 12 mpg. That is after accounting for the 6% odometer error with the larger-dia. tires.

 

I stopped calculating my MPG's after the first few times post-lift and 275 install. I hurts to know how bad it is now. Pre-lift was 21-22 245's post lift with 275/70 (32.2") is 15 WTF?

 

^No way you were getting 21-22 mpg before, unless it's all highway 65 mph with cruise control.

 

Hehe. Nothing wrong with that either after you have a baseline. I'm just adjusting my budget for the beginning of 2014 and planning mods. Really want to know what a lift and tires is REALLY going to cost over the course of a few years.

"If you don't plan, you plan to lose."