3mpg mileage drop

[mjoekingz28]

Hey I just put on some Uniroyal Tiger Paw Touring tires in replace of some 9yr old Kumho 732 touring tires. The TPs are H rated while the Kumho was T rated and now I'm down to 37mpg from 40mpg.

Same inflation of 32f/28r (30/26 on door) and did the same 300 mile route as I always do and used 8 gallons instead of the usual 7.5 gallons.

Can going to a different rated tire cause this? At first I thought it might be all the extra tread weighing it down, but I had gotten 40mpg for the last 20-30k miles on the Kumhos. It feels like the car has to work harder going up hills now, but at least everything is smoother (aka no steering wheel twitching).

I spent like 2 months studying which tire to get and mpgs never crossed my mind, but this extra half gallon a day is $1.25x5 days a week= $7.50X50=$375 which is what the tires cost and will effectively double the purchase price.

This sucks!

 

[Mr Nice]

New tires usually have more rolling resistance.

 

[willix]

Bump it 2 lbs per axle.

 

[Chris Meutsch]

Agreed with both above posters.

 

[Eddie]

Agree with above. However; a one tank check is not a reliable number. I drive the same route the same way day after day and keep acurate fuel consumptions. I average 21.32 mpg but, with a standard deviation of 0.8 or a 3.8 % veriation and this over 20 tanks of fuel.

 

[Geo_Prizm]

I had been using Kumho Touring tires on my car till last fall, I replaced them with Yokohama Avid TRZ tires, instead of seeing a fall n MPG I have observed increase in MPG. And TRZs are made in USA.

 

[JHZR2]

do 5 tanks and come back to us with the averages cross all of them.

 

[sparkplug]

Wanna trade gas mileage?

 

[JimPghPA]

Even if you used the exact same tire, the rotation inerta differance from a worn tire with much less rubber on the outer most section vs a new tire with much more rotation mass will cause a decrease in MPG. The energy you put into getting that mass rotating all 4 tires is lost when you brake. And new tires waste more energy in this process.

It is kind of like running in winter boots vs running shoes.

 

[IndyIan]

You do 300 miles a day? That is alot of trucking!
As for your mileage drop, some of it might be from increased diameter of the new tires? Did your drive get shorter by a few miles?

 

[tomcat27]

are the tires the same size?

 

[mjoekingz28]

thank you all. I will bump it to 34/30psi and keep track this week if I can. It was mild yesterday so I didnt have to run the AC, maybe the rest of the week will be like that and I can get good readings.

sparkplug, wanna trade power? 124hp.... Barely gets me up steep hills under 3000 rpms

eddie, this deviation was more like 8-9%, I get what you do I guess, I cannot convert 39-40.5 into percentage but it seems to be about 3%.

 

[JustinH]

Sounds right to me. I lost about 3mpg going from bald firestone tires to new goodyear all seasons.

Its a good price to pay for traction, and safety.

Keep the tire pressure where the factory recommends, unless the tires are wearing out too early.

Remember, the tire pressure also affects suspension components. I'd rather buy tires before suspension parts.

 

[odie]

we keep tires 2 > 3 p.s.i. over the recommended pressure for car . JustinH , agree tires are part of suspension and find it crazy running tires at 40 p.s.i. or higher for gain in mileage . Just asking for a more expensive fix to the suspension than the savings in gas .

 

[SteveSRT8]

normally new tires will cause such a small change in rolling resistance it should be VERY hard to actually quantify.

X2 on the suggestions to experiment with tire pressure. You may just have had a bad load of fuel or changed environmental variables.

 

[daves87rs]

Have to break those tires in first..

 

[carwreck]

You have a new special "matched set" of tires...
you are driving faster through turns and accelerating harder to test the new tires.

Even if you were driving exactly the same, your odometer is no longer measuring a mile the same as on your previous tire. Different brands of the same size tire can vary by 1/2" on the outside diameter.
Your speedometer cannot adjust for this change, and can be off by 2%.

---------------------

1999 OLDS GLS

 

[The Critic]

Originally Posted By: JustinH

Remember, the tire pressure also affects suspension components. I'd rather buy tires before suspension parts.


Suspension repairs aren't always expensive these days. Which suspension parts could be damaged? Tires probably cost more than your suspension repair.

 

[mjoekingz28]

Alright, BITOG we're starting to cook.

Ran 'em up to 34/30 and got 38.5 today which is 1.5 better. The ride is a little more busy and wanders a little more easily but is a good ride and almost feels like Im floating.

Checked the tripmeter and it looks like I'm about 3 miles under (297 vs 300).

I don't know if they're broken in yet, there are 1200 miles on them so far. Today it felt alot better going up hills. Its as if Im not riding through slush anymore.

2 psi proved itself very well today.


Yeah, Critic.....I saw the Richpin video on ball joints and the only difficult part is getting that chain affixed to the sway bar and taking the tension off. Also, I read on Saturnfans that tie-rods just screw in and screw out....although I've never done suspension work aside from chaning shocks on a Dodge Dakota once.

 

[PandaBear]

Some tires have weak sidewall that you need to compensate with higher pressure (i.e. Sumitomo HTR200), but if you do, they are very fuel efficient.