Instant mpg gains with new tires?

fishguy1123

Original poster
Member
Dec 5, 2011
310
I just bought new fortera hl's yesterday. They replaced the michillin cross terrain's that were worn to the wear bars. I left the dealership and drove about 40 miles mixed highway (70-80mph) and rural/city driveing. I reset my dic before I left (I know it's not accurate). However, my normal math calc mpg's are around 19-20 similar mixed driveing (dic reads 3 mpg higher). By the time my trip was done the dic read 25.2! If this is what the future holds, that will make an instant 2+ mpg increace. :biggrin: I know tires can make a difference both up and down in the mpg's but, what have you guy's found when replaceing "similar" type/size tires?
 

jbones

Member
Dec 5, 2011
658
fishguy1123 said:
....By the time my trip was done the dic read 25.2!?

Your getting 5.2 MPG more Highway?


2002 Trailblazer
EPA Fuel Economy
Miles per Gallon Regular Gasoline

16 Combined 14 City 20 Highway
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
It was a mix of both hwy/rural-city. I'm sure the 25.2 on the dic was a good 3 mpg more than the actual but I've never seen it go that high before the new tires. The 19-20 was by doing the math a couple months ago. I'll fill up and start the math method again today and see what happens.
 

Uncle Blazer

Member
Dec 8, 2011
263
Must have been the Nitrogen they put in the tires :rotfl:

but seriously, let us know what your actual mpg turns out to be
 

DocBrown

Member
Dec 8, 2011
501
Tires can have a dramatic effect on mileage. Mine dropped by about 1.5 MPG when I put the Firestone Destination LEs on. I found that by bumping the PSI up 3 lbs I made up for most of the lost mileage.
 

ElAviator72

Member
Jan 11, 2012
118
Also worth mentioning that the Fortera HL's have a very thick, beefy tread, so it is possible that the tire diameter is somewhat larger than stock (for the moment). If that is the case, expect that advantage to disappear as you drive the tread down :wink:

How many miles did you get out of your Michelin X-terrains? We only got about 40,000 on ours before the tire shop started warning us that they were worn down, and I put about another 10,000 on them after that. We changed to the Fortera HL's when I had the snow tires taken off this spring, and the Michelins were down to the wear bars. Those had to be the worst Michelins I've ever owned for longevity :frown: And they had severe weather checking problems at only 3 years of age, too (granted, we did buy the truck used with 23,000 miles, and it came from Nevada).
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
ElAviator72 said:
Also worth mentioning that the Fortera HL's have a very thick, beefy tread, so it is possible that the tire diameter is somewhat larger than stock (for the moment). If that is the case, expect that advantage to disappear as you drive the tread down :wink:

How many miles did you get out of your Michelin X-terrains? We only got about 40,000 on ours before the tire shop started warning us that they were worn down, and I put about another 10,000 on them after that. We changed to the Fortera HL's when I had the snow tires taken off this spring, and the Michelins were down to the wear bars. Those had to be the worst Michelins I've ever owned for longevity :frown: And they had severe weather checking problems at only 3 years of age, too (granted, we did buy the truck used with 23,000 miles, and it came from Nevada).

I wish I could tell you the miles on the Michelins, came with the tb from the PO when I got it. I knew they were low on tread and put another 11,000 on them to get through the winter (August-now). I filled up today and will track the mpg until I fill up next time. I also need to check the tire pressure (my guage sucks and need a new one).
 

Jkust

Member
Dec 4, 2011
946
Interesting. I've got the Fortera HL's on the Rainier and not on the 9-7 and the identically equipped Rainier gets a few mpg's better on the highway and have never been able to figure it out. It never dawned on me that tires could be the difference. The HL's are pretty beefy. I routinely get 24 and change on the highway with the Rainier at least on the DIC and the 9-7 just doesn't get there. The other side however to the above situation is the Rainier gets much worse city mileage than the 9-7.
 

ElAviator72

Member
Jan 11, 2012
118
Jkust said:
Interesting. I've got the Fortera HL's on the Rainier and not on the 9-7 and the identically equipped Rainier gets a few mpg's better on the highway and have never been able to figure it out. It never dawned on me that tires could be the difference. The HL's are pretty beefy. I routinely get 24 and change on the highway with the Rainier at least on the DIC and the 9-7 just doesn't get there. The other side however to the above situation is the Rainier gets much worse city mileage than the 9-7.

Do they have the same rear end gearing? Is the SAAB full-time AWD like the Rainier? If one has different gears, that could also help explain the mileage difference...:wink:
 

Jkust

Member
Dec 4, 2011
946
ElAviator72 said:
Do they have the same rear end gearing? Is the SAAB full-time AWD like the Rainier? If one has different gears, that could also help explain the mileage difference...:wink:

Yes they are identical aside from all the SAAB suspension tweeks and the SAAB has the G86 limited slip that the SS adopted. The Rainier and SAAB only came with the 3.73 rear end if they had the optional 5.3l. They are also both full time on demand AWD as well. Basically the same vehicle but the SAAB wheels are 1" larger and also a lower profile tires.
 

gr82bCanadian

Member
Dec 8, 2011
74
This is wonderful information :thumbsup: since I'm looking into new tires soon :biggrin:
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
I also have 3.73 gears as well. I should be able to get the first tank mpg's in a couple days. Unfortuinately I'll be towing a utility trailer on sunday so that will muck it up a lil.... :mad:
 

Jkust

Member
Dec 4, 2011
946
fishguy1123 said:
I also have 3.73 gears as well. I should be able to get the first tank mpg's in a couple days. Unfortuinately I'll be towing a utility trailer on sunday so that will muck it up a lil.... :mad:

Yep towing tends to mess up the calculation. Even towing just my two snowmobiles plus two place trailer kills the mileage especially in town.
 

MacMan

Member
Mar 3, 2012
194
fishguy1123 said:
Funny you mention the nitrogen.... My old set had it in them, these don't! :smile:

Just another reason to stay away from that tire shop/dealer "nitrogen in your tires makes it run better but we make a lot of profit making you think you need it" nonsense. :mad:
 

Jkust

Member
Dec 4, 2011
946
I just checked and my 9-7 does have Forteras but they are Triple Tread not HL. The Triple Treads are $220 a pop which is a good bit more than the Rainier HL's that are an inch smaller but the Triple Treads are slightly more noisy. But it seems as though the Triple Treads each have different amount of even wear plus one of them I think the one with the least tread needs balancing or is just bad so the sound comment may be due to that. I'm going to say the 9-7 has maybe had a couple flat tires replaced given some are like new and the bad one is almost at the bar. The Tripple Treads just look cooler though. Truth be told i've never had good luck with any Goodyear tires since they always seem to wear faster than even cheapo's but they always seem to come on the cars I buy.

Edit: I just checked and all 4 or the 9-7x tires were manufactured 31 09 so they just wore incorrectly.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
At 220 a pop I could buy 2 sets for what I paid for the hl's... My main concern with the hl's was tread life, but at the price it seemed like the right choice for me. I've notice a huge improvement in ride quality but campared to old tires that's to be expected. I didn't set out to gain mpg's with the hl's, but if it helps I'll take it. Jury's still out though.
 

Jkust

Member
Dec 4, 2011
946
fishguy1123 said:
At 220 a pop I could buy 2 sets for what I paid for the hl's... My main concern with the hl's was tread life, but at the price it seemed like the right choice for me. I've notice a huge improvement in ride quality but campared to old tires that's to be expected. I didn't set out to gain mpg's with the hl's, but if it helps I'll take it. Jury's still out though.

Just looking at the tire rack site, the HL's didn't show up for the saab with the larger/lower profile tire requirement so it's not really apples to apples but the 17" HL's were still more than half the price. I think I'm going to need new tires for the 9-7 within the year just to smooth out the ride but I really hate to blow a grand on rubber. The HL's on the Rainier have maybe 5 or 6,000 miles on them so I really can judge their life, but I've had other Goodyears last half as long as the cheapest/generic brand tires on the same vehicle. Happened when I got a couple blow outs on the minivan and got a head to head comparison of GY's compared to some crappy General brand and the Generals lasted way more than twice as long. The Goodyear's were disgraceful.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
I have no clue what the 9.7's require, but I paid 530 otd for the hl's. So, like I said for me it was the right choice. If I get 45,000 out of a 60,000 mi. rated tire I'll still be ok with that at the price I think. I've heard ppl say some of the brand/models they bought at twice the price didn't last like they should either... We'll see.
 

Envoy09

Member
Mar 26, 2012
57
You guys really get around 20-25mpg, which is around 8.5-10.7km/litre? Any idea why I get only around 7.5km/litre even though I drive mainly on highways. This was the case ever since I bought the envoy brand new. I have now changed to Goodyear Eagle F1 Asymmetric from the Dunlops & I still get the same 7.5km/litre. Strange.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
Well, the 25 number I mentioned was on the dic. It always reads higher than actual, for me about 3mpg higher. Which means yes, 19-20 mixed driveing average by doing the math at my fill ups vs. miles driven. I'm not sure if the environment would affect you where you are to cause that kind of mileage or not. The most common mechanical reasons could be dirty throttle body, bad thermostat/temp sensor. It could depend on what gear ratio you have also. If you're an agressive driver and like the skinny pedal that wont help either....:rotfl:
 

Jkust

Member
Dec 4, 2011
946
fishguy1123 said:
Well, the 25 number I mentioned was on the dic. It always reads higher than actual, for me about 3mpg higher. Which means yes, 19-20 mixed driveing average by doing the math at my fill ups vs. miles driven. I'm not sure if the environment would affect you where you are to cause that kind of mileage or not. The most common mechanical reasons could be dirty throttle body, bad thermostat/temp sensor. It could depend on what gear ratio you have also. If you're an agressive driver and like the skinny pedal that wont help either....:rotfl:

Luckily the 5.3 liter doesn't have the dirty trottle body issue and the thermostats are right on the mark too. Interestingly enough, I've purposefully driven agressive and really light on tanks to compar and the manual mpg calculations are very close. Regardless, I will keep mpg in mind when it comes time to change the tires out.
 

fishguy1123

Original poster
Member
Dec 5, 2011
310
Well, 1st tank numbers were 17.75 mpg by math and 20.7 on the dic. That includes 65 miles of towing a trailer (5x9 utility to empty a storage unit) which was rural/city stuff in 3rd gear. As I said before, my dic seems to be almost exactly 3 mpg's more than actual.
 

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