Gas Milage

[Desert Rabit]

Hello,
I am only getting 11 miles on a gallon of gas on average with City driving without AC on. I used to get close to 15-16 miles/gallon. I have a stock 97 Lexus 450. The only non-stock item is the tire which is 285/75R16, a little heavier. I had a new air filter installed. IT did not help much. Next step is inflate the tire a little more. Any suggestion? Thank you.

 

[mjosoba]

That’s about 2” over stock size. So heavier and taller, both will impact your mileage. So there’s that. Also, are you adjusting for that in your mpg calculations? It will be X% off. Not sure the exact number, search will help.

 

[asuddendeath]

O2 sensor would be next

 

[shocktower]

Sucking it up and realize this ain't no Prius , and 11 is not bad

 

[Rifleman]

Before you throw anymore money at this problem you might what to make sure your running the right amount of air pressure in your tires.

Anytime you change tires from stock street tires to off road tires you can end up with a softer tread compound plus a larger contact patch.

That softer compound and larger contact patch can add to increased rolling resistance, which can/may lead to lower gas mileage.

Just as a point of interest, when i changed from street tires to off road tires (same size as my stock street tires) i went from 12 MPH around town to 10.

This was all due to the fact that my new off road tires were made out of a much softer rubber compound then my old street tires were.

Below is a link to a real good thread that'll help you adjust your tire pressure to get the best wear/mileage.

Tire pressure question?

forum.ih8mud.com

 

[MoJ]

Is your heater working?

 

[Tanner H]

Honestly my theory is your 15-16mpg calculation was off. 11 with 285's sounds spot on.

However for peace of mind I would clean your MAF if it hasnt been done in a while/ever.

Might as well check all your fluids. diffs, and transmission. anything that is supposed to be lubed can cause excess friction and kill your mpg.

 

[rolliges]

My 97 at around stock weight with BFG KO2 285's gets an adjusted 14-14.5 mpg. on the Hwy.
Tire pressure usually between 36-40 psi.

I take fairly good care of it. Rear O2 sensor is original; front is a new Denso. Everything that needs oil or grease has it.
I drive with a light foot.

 

[Cruzerman]

No offense, but this rig was only rated at 12 city and 14 highway. It seems unlikely to me that you used to get 16 mpg in all city driving.

 

[sbman]

Yep, the EPA rating was 12 city and 14 highway as @Cruzerman said.

That being said, when I was all stock I did manage 16 on a couple of freeway only trips. I was down to 10 for a while with an RTT up there and seem to be back to about 12 for combined city/highway with the RTT stored in the garage, thats on LT285/75R16 @ 38 psi, an add on bumper, winch, dual battery and aftermarket roof rack, and correcting for speedo error with the larger tires. I really don't do any better than 12 on the highway though.

 

[zapatius]

I get 12 with a trailer, without a trailer, with A/C, without A/C, in town, highway....doesn't seem to matter. Nitto Terra Grapplers, LRE, at 45 PSI.

If you were getting 16, something wasn't correct.

 

[baldilocks]

No offense, but this rig was only rated at 12 city and 14 highway. It seems unlikely to me that you used to get 16 mpg in all city driving.

Actually 13/15 but yeah....

 

[asuddendeath]

Im getting under 10 right now 37's 5.29's but its also has a turbo and I can keep my foot out of it.

 

[LINUS]

Call it a day & be fine with it.

Most of us get 10-11 combined, just the way it is.

If it idles right & all the metering of air/fuel plus your ignition side parts are reasonably decent condition, it’s just life.

You never stated when you thought you were pulling 16, but 11 is realistic compared to the idea of 16.

If that doesn’t satisfy you, switch gasoline grades / run some fuel treatment & check the injectors / swap your fuel filter if you never have.

 

[Desert Rabit]

That’s about 2” over stock size. So heavier and taller, both will impact your mileage. So there’s that. Also, are you adjusting for that in your mpg calculations? It will be X% off. Not sure the exact number, search will help.

Very good point. Thank you. The circumference of 285/75 is 1.0537 x of 275/70 R16 tires. Taking this into account I am getting just over 13 miles/gal which makes me feel better.

 

[AlpineAccess]

People track their gas mileage?

 

[Adrock]

I'm averaging 15.5-16mpg in my 97. Stock gears with 315s. Commuting over the coast range. Compensated using gps mileage.

That said, I get 10% more than most people with my diesel Cummins on this route too. I drive pretty mellow and its all 60-65mph on cruise the whole way.

 

[Desert Rabit]

Thanks EVERYONE all for the suggestions. It does not seem mine is much worse. It is an old vehicle and has over 140K miles now. BUt I like it. As it gets older things start to fail. I recently spent nearly $600 on a reputable shop to install a new EGR modulator valve and cleaning the passage. A new door actuator is $200 plus just for the parts, it is getting expensive .... Anyone knows a reputable online source for parts?

 

[fz1boxer]

Thanks EVERYONE all for the suggestions. It does not seem mine is much worse. It is an old vehicle and has over 140K miles now. BUt I like it. As it gets older things start to fail. I recently spent nearly $600 on a reputable shop to install a new EGR modulator valve and cleaning the passage. A new door actuator is $200 plus just for the parts, it is getting expensive .... Anyone knows a reputable online source for parts?

norwalk toyota never let me down great prices and fast shipping,i get stuff quicker from them than i get from the 2 local dealers,10 miles away.

 

[musthave]

Get one of these. Cheap mod gives you another 15 mpg or maybe more.

Seriously though, tires, O2, adjust gor tire size. Drive it.