Tire size and fuel mileage?

Folks-

I've been able to do my first MPG tests on my rig now that I've used a tank a gas up. Seems like I'm getting around 15 MPG, strictly city driving, in an '87 4X4 LE auto.

This seems on the low side, is it? There's no weight in the van, she runs like a top, passed DEQ very nicely.

I got to wondering, are the 195R14's I'm running make my odometer read a little differently? I know these were set up for 205's so I'm not sure how much of a difference that would make. Oh, the tires are brand new Hankook light duty truck tires, so I know as well new tires lower MPG too?

We're about to take this baby across the country, and I just paid $3.50 a gallon for gas, ouch!

mark in Portland

Tire size difference is nil. The Nankooks are so close to stock size they will only throw off the speedo by about 7/10th of a percent (that's less than 1/2mph when traveling at 65mph). Also those tires are not very aggressive so I doubt the tread has much (if anything) to do with it. Did you ever check mileage with the old tires? How much pressure are you running in them?

If the van passed emissions then that's a good indication it's running efficiently and the sensors are good. Did it pass with flying colors or did it just squeak by?

Any roof racks or add-ons to disrupt air flow? Are you easy on the throttle or do you enjoy jack-rabbit starts?

I assume it's being used in 2wd and the hubs are unlocked. If it's got automatic hubs make sure the 4wd light on the dash is out. If it's on try backing up a few feet with the switch in the off position.

All things considered, you should be getting better than 15mpg (even around town) but around town in Portland could be the problem. I know from personal experience you can end up sitting in one spot for long periods. It becomes so normal it's easy to forget it even happens. The best way to gauge fuel consumption is to go on a road trip. A 4wd auto running in 2wd should get around 20 - 25 on the highway. While you're out there check your odometer. Use a GPS or simply watch the mile markers go by. Go at least 10 miles to maximize accuracy. If you pass 10 mile markers and your odometer says you only went 9 miles, then you either counted wrong or your odometer is off :wave2:. Tim

I haven't checked the pressure in my tires since they were put on, I need to do that. They look fine though, they don't look low or I woulda filled 'em up.

We are taking a trip to Astoria tomorrow so that'll give the van a chance to stretch out a bit on the highway. We'll see how the mileage ends up being, and, I can check the odometer accuracy too.

Someone mentioned they get better mileage with higher rated gas. I've always doubted that, but, I'm also running the cheapest gas possible and of course it has ethanol in it too.

mark

Cheap gas can do that. It's all about BTUs per gallon. If you're running fuel that's lacking in BTUs it's going to take more of it to get the same job done. Of course there's really no way for the average consumer to evaluate fuel quality. All you can do is try to avoid the really cheap stuff and gas with high percentages of ethanol. Due to high engine compartment temps, these vans are a bit more sensitive to cheap gas. I hate to say it but the truth is you may end up getting the same stuff even when you pay more. Enjoy your trip :)>:. Tim

Here's a related thread: http://www.toyotavantech.com/forum/s...ion-effect-MPG

FWIW I have the same 4x4 a/t van. My engine is new and everything else functions flawlessly and is dialed in to factory spec. I do flatland highway trips every weekend with an 18' ocean kayak on the roof frequently. I have never broken the 18mpg mark on these trips. I get 16-17.something mpg at best. I travel around 60-70 mph on the highway but even when my cruising speed is mostly below 50 I still don't break the mpg barrier. I have used 91 octane since birth but recently switched to the cheap stuff with no difference in mpg, just a little pinging under certain conditions. I am running taller tires (bfg 215/75r15, around 29" tall) but my mpg calculations take this into consideration. I am in CA and the gas here sucks. I blame much of my issues on that. Nevada gas gets me a lot better mpg on my other rigs but I haven't tried it on my tv yet.

Smaller tires will register on the odometer as MORE miles than actually traveled, so your van's mpg is actually worse than calculated.

FWIW, my 4WD has 205s and the odometer is virtually dead-on.

Time to start examining driving habits ...

Gwen

My '87 4x4 auto gets about 19 MPG. I use it in the winter, in South Lake Tahoe, so I buy California and Nevada gas. I don't really see a big difference between them. I've gotten up to 24 MPG (one time), but usually use 20MPG when doing the math (trip meter) for refill time and that's never given me trouble. We go to the ski hills, so up and down mountain grades and run around for groceries, etc. Occasionally, we'll head off the hill and down to the Bay area. 80 MPH + on the freeways down there still ends up close enough to 20 MPG

We travel back and forth from CA to Minnesota, seasonally, and I've noticed significant differences when ethanol starts getting involved. That's been my reasoning, although I suppose it could be wind, traffic, etc. We've been doing this since the 90's, so this happened with both of our '87 4x4 auto TV's, a '92 Caddy and the last several years our '97 Subaru. All of those vehicles seem to vary, but it's closer to a 10% or 15% difference (18 - 20 TV, 22 - 26 Caddy, 26 - 30 Subaru)

25% less than the average TV is significant, but some of it may be local gas and some driving habits. That ethanol may be a culprit.

Definitely ethanol enters into the equation ... I always get great gas mileage in Wyoming (despite the high winds), for instance.

BUT ... I have no choice but to run E10 — state law. Well, unless I want to convert to E85 (no thanks). Even at that, I'm getting 25-27 mpg commuting (mostly highway miles) in a 5spd 4WD (with 328K), and 28-30 on road trips. I wouldn't dream of expecting that from an automatic, but it does show that decent fuel economy can be achieved on E10, and it implies that 20mpg or less is not likely maximizing an automatic's mpg potential.

Gwen

Well I did a nice day trip to Astoria in the van a few days back and was able to monitor the MPG on the highway, some big hills, some traffic.

21.6 MPG.

Not too bad, I'm not sure why the last city tank was so low, but I will continue to monitor!

mark

That's not too bad.......for that stretch of road pretty average from my experience. You could probably squeeze a couple more out of it if you are willing to piss off the people behind you. Of course impatient people do crazy things so I consider it safer to to just go with the flow and spend a little extra at the pump. Tim

I just drove from here in N. Idaho to Florence on the OR coast, 1250 mile trip total. I had been getting about 19 on the hwy with the yakima bars and ski rack attachment on top. I took all that off for this trip (totally smooth) and averaged 21-22 mpg driving 65-70 mph most of the time. I think even a little disruption of our svelte(ha) aerodynamics can affect mpg. NEC I bet w/out the kayak on top you would see at least a 3 mpg improvement. In my experience with these rigs, aerodynamics seems to make a much bigger difference in mpg than passenger/cargo weight.

Last summer I had TWO canoes on top for a trip to Glacier Park. I only figured the mpg once (15 I think) and didn't bother after that. I also couldn't help from dropping to 45 mph on a few grades - it was terrible! One of the problems is my bars aren't wide enough to fit two canoes flat side by side so the gunnel of one was propped up on the hull of the other, so I imagine air was slamming into the upper canoe with no where to go

Hi everyone,

I've just started putting some milage on the zebra (88 2wd MT) with a trip to reno and a couple of trips to the desert. I was running some weak tires, 195r14 with about 1350lb capacity on each with snow tires on the back. These tires were bulging under the load of the zebra but on the reno trip I averaged 24.5 mpg over the whole trip. I've just changed out my tires with Load Range D tires, I put the Nanking 801's in the front, For the rear I got Radar 878's from tires-easy a little more aggressive tread than the nankings and I'll use them for the front in the winter with snow tires as the drive tires. I'll see if this changes my milage later this week on a trip to sacramento.

Sean