Fuel mileage.

[Cubey]

Argh! I am bad about checking tire pressure often. It's been almost 3 months. They have all lost almost exactly 10psi. For the rears, that puts them at 70. I like them at 80, tire max, instead of 65 that the RV conversion tag calls for. Some of you might remember the whole "65 psi max rated dually rims" thing back in August or so. Anyway, 70 is fine, it's still over the spec.

But i had the fronts at 70. Now they are 60 from the 10 drop. That IS under the 65 spec.

Gonna go get Walmart (a mile away) to inflate my tires to 70 front/80 rear again since there's no free air hose around, and I need to get angled extensions for the outer rears for using a 12v air compressor. I can't reach the stubby valve with the fitting on 12v compressors. Inners already have extenders so they aren't a big deal.

So, the point of that long winded post is that those 60psi front tires is probably where my mpg went. 70 rears probably don't help either. I get the best mpg with at least 65 in front and 80 rear.

 

[chillman88]

@Cubey Make sure to check your lug nuts after Wally world touches it. Sure they should be fine but I've learned to not trust them as far as I can throw them! Beats having an assumption come back to bite you!

EDIT: Had them mount the spare for my dually. They said it was done. Picked it up and it had about 20PSI in it.....

 

[Selahdoor]

Checked my odometer again today.

Seems to be correcting itself.

Now, instead of losing as much as it seemed to the first time...

In the same six miles. .4 for the first three miles. Then .3 for the last three miles. (For example 1.4, 2.4, 3.4, 4.3, 5.3, 6.3)

Now that COULD be explained as, my odometer is now bang on correct... And the "mile" between mile 3 and mile 4, is actually one tenth less. So, we'll see. I'll keep checking whenever I get the chance in other places.

Also, the speedo didn't jump around as much as it was, And the 'drag' seemed less. Like maybe the bearings had rust on them from sitting for 5 years... And the more I drive it, the more things will loosen up.

 

[Cubey]

@Cubey Make sure to check your lug nuts after Wally world touches it. Sure they should be fine but I've learned to not trust them as far as I can throw them! Beats having an assumption come back to bite you!

EDIT: Had them mount the spare for my dually. They said it was done. Picked it up and it had about 20PSI in it.....

I had a Walmart install the tires where I had them sent. I watched them torque all the lug nuts by hand.

This Walmart is too cramped to deal with this RV, but the tech told me where to find a free air hose in town, so I'll go over there tomorrow.

 

[rustygold]

And then?

Haven't had check it again because shortly after i did that i pull heavy stuff and had to plucked the motor.

Sent from my SM-G892A using Tapatalk

 

[Selahdoor]

Ah. Ok, thanks.

 

[Shadetreemechanic]

My next thing to improve mileage is going to be to change oil weights in the IDI. I just replaced the 15-40 in my mercedes with 10-30 and we picked up 2.5 mpg.
My guess is that the change will be less dramatic on a 7.3 liter engine than it is on a 3 liter one, but I am hoping its noticable.

 

[Cubey]

My next thing to improve mileage is going to be to change oil weights in the IDI. I just replaced the 15-40 in my mercedes with 10-30 and we picked up 2.5 mpg.
My guess is that the change will be less dramatic on a 7.3 liter engine than it is on a 3 liter one, but I am hoping its noticable.

From what people say who bought these new, IDIs were oil burners right out of the factory. You may find that your oil consumption skyrockets with 10w30, especially at the age of IDIs now.

 

[chillman88]

From what people say who bought these new, IDIs were oil burners right out of the factory. You may find that your oil consumption skyrockets with 10w30, especially at the age of IDIs now.

I didn't notice much of an oil consumption change with 10w30 in mine. Just an fyi. Mine seems to devour about 1qt every 500 miles or so.

 

[Cubey]

I didn't notice much of an oil consumption change with 10w30 in mine. Just an fyi. Mine seems to devour about 1qt every 500 miles or so.

Oh? interesting. My RV, being under 100k original I highly suspect, doesn't burn as badly as my F250 which is probably 150k-250+. If 10w30 gave my RV a 1-2mpg increase, I'd switch to it for sure. But I doubt it would.

 

[chillman88]

Oh? interesting. My RV, being under 100k original I highly suspect, doesn't burn as badly as my F250 which is probably 150k-250+. If 10w30 gave my RV a 1-2mpg increase, I'd switch to it for sure. But I doubt it would.

I don't know that I'd want to run 10w30 where you are. I don't know if the IDI charts cover it but the powerstroke viscosity charts say 10w30 is ok up to 90 degrees ambient temp, but recommends 15w40 above 10 degrees ambient temp. I try to only run 10w30 in the winter.

That being said, I think the last couple weeks it's been warmer up here than some places down south!

Yes, you should be FINE and I'm sure people will argue not to worry about it. That being said, I'd rather risk a slight economy hit if it's protecting the engine better. Just my opinion though.

 

[Cubey]

Yes, you should be FINE and I'm sure people will argue not to worry about it. That being said, I'd rather risk a slight economy hit if it's protecting the engine better. Just my opinion though.

1-2mpg is a roughly 11% to 22% increase in the RV. But I agree on better engine protection with 15w40, so I will stick with it.

 

[Shadetreemechanic]

My mercedes has 448K on the original motor. I was very concerned about burning more oil, but it just wasn't an issue. We just got back from a 2,300 mile road trip and burned 1 pint of oil. That's really no different than what it burned with 15-40.
Mileage on that trip was 26.6. Generally with that car its 24-25 on the highway.
Like I said, I can't imagine it will change things that dramatically in my IDI. I just put 15-40 in it so I won't get to try this winter anyway.

 

[Selahdoor]

Ok, changes in the truck recently amount to unplugging the RABS module, swapping on the snow tires, and it does seem the bearings have loosened up more. (Although it has started a hum that sounds like the bearings need to be replaced.) It coasts better than it used to.

Snow tires are smaller than the summer tires. Difference between them is that the taller ones roll 619 times in a mile. And the smaller ones roll 662 times per mile. Roughly a 7% difference.

Ok, so the mileage on this last fillup, when adjusted for tire size is ~22 MPG.

That's as good as my camry.

I am not going to state that as the official number just yet.

I want to see that number more than half a dozen times, before I make it official,

 

[chillman88]

Ok, so the mileage on this last fillup, when adjusted for tire size is ~22 MPG.

That's as good as my camry.

You know you're not supposed only figure your mileage while coasting downhill