Lift Kit or AT Tyre Swap Missing MPG?

[Miner]

As above... just lifted the car 2” and fitted AT tyres... run the car lifted for a week and didn’t notice any discernible drop in MPG... now swapped the 265x60x18” Dueller 840 HT’s for 265x70x16” Geolandar AT-S rubber and the fuel economy has taken a massive dip. Still trying different runs to get a mixed reading but anywhere between 2-4 or more MPG....

Is this normal / expected? Was expecting a drop but not that much.... thoughts? Car is 2011 SWB 3.8L Pajero 4-3.

Pressures are ok, tyres are new, alignment has just been done post lift (including replacing all front and rear alignment bolts as all were seized to some degree) and post tyres... steering not 100% though, don’t think they’ve balanced the toe properly, wheel isn’t centred, centering properly... mrs picked up the new rubber and final alignment. Trust the shop but it was late on at the end of the week. I’m getting the rear lower arm inner bushes replaced tomorrow (took a beating getting the camber bolts out them, car done 170k km so swapping out on both counts). Will get the alignment checked again also where I can witness it.

Appreciate your feedback.... wont be rushing to offload my 18’ as it stands, might treat them to new Geolandar HT’s for highway use in between dune bashing trips.

[old Jack]

Yes and Yes!

Even though both the tyre's you have quoted have the same rolling diameter, a more aggressive tread will consume more fuel, if the tyre is also physically heavier, such as when you go from a passenger construction tyre to a light truck construction tyre you will use even more fuel. About 1/2 to 1 litre per 100kms it what I would have expected but if you had gone up a size, gone the 10ply LT's and to a very aggressive tread tyre then it could be as high as 3 litres per 100kms!

Raising a vehicle by suspension lift alters the aerodynamics of the vehicle, it has little impact on fuel economy under 80kph but once over 80kph the effect increased significantly with speed increase.

OJ.

[nj swb]

I went looking for tyre weights, and couldn't find specs for your Geolandar.

Your 18" tyres weigh 38 pounds each (sorry, US websites are better at listing weights than Australian sites), and a LT tyre similar to your Geolandar might weight 48 pounds each. That's an extra 40 pounds of tyre that you're accelerating every time you push with your right foot, which will require extra fuel.

It's not just the equivalent of lugging around an extra 40 pounds in the back seat - each tyre will be harder to "spin up" as you accelerate, so you get a double whammy.

Then, because your petrol shorty has such a good power to weight ratio to begin with (compared with us driving lwb diesels) the extra weight / resistance has a more pronounced effect - you've effectively added a higher percentage of load to your original configuration.

If you're having that much fun, you've gotta pay for it.

[Having Fun]

My wife's old NP running the 3.8 had 17" HT's on it when she got it & the best it would do was around 16L/100km.

When we swapped the HT's for heavier AT's, nothing changed around town, she still gets 16L/100km (it's actually better on fuel on dirt roads with the heavier AT's on it, we got 12's down the Plenty Hwy)

I'd be looking hard at what was done during the alignment!

[Miner]

no pain no gain...

Starting with the alignment, I’d like to assume that they just quickly adjusted to green and knocked it off when locking it up as it was late at the end of the week... as I’ve used the shop for a while and will again but it was miles out. I usually stand in and around the pit till its done. Went to get it re-checked at a 4x4 specialist near the garage in Dubai I went to to get my rear arm bushes done and wasn’t impressed with what I saw, sums up how it felt. It has improved the economy a little, was pulling and steering could be best described as darty. All good now. A little less noisy too.

Makes sense regarding the above... when I felt how light the 16” OE Enkei’s were I thought I was onto a winner... didn’t get to feel the new AT tyres before they went on, like to check these things. Will suck it and see.... mrs says we’ll never be ready for an early weekend dart if I’ve to got get home late and swap the wheels, so just leave it. See how it pans out.... looks good.

Conversely though that’s the least amount of fuel I’ve ever used off-road.... so much more traction, so much less fuel burnt... save the planet one trip at a time and burn the ozone the rest of the week going to work.

[Miner]

For info....

https://www.yokohama.com.au/our-range/tyres/geolandar-a-t-s-g012