I am a new member to your forum and was wondering if you could give me some insight as to your opinions of the powertrains listed above.

I am currently in the market for an H3 for my wife and have not yet been sold on the V8. Is there that much of a performance difference? How does the mileage compare?

 

I cant Help you Mattroanai...I have a 07 H3 Hummer with the Inline 5..3.7 and I just added theVOLANT Air Kit and next week Ill be installing the VOLANT CatBack Exhaust...Then I will check my gas milage and HOPE I get close to 20 mpg...I bought mine used and have NO CLUE what type of milage I get cause I havent drove it much yet.I was going to get a V-8 till I seen the milage reports so I stayed with the Inline 5

 

I had a 3.5 now have a 3.7 both with Magnaflow Catback exhaust and Airdoc CAI and recently drove a loaner Alpha for a week. Here are my observations. There is a noticable difference between the 3.5 and the 3.7 as far as power goes. Gas mileage is about the same. I got around 15 MPG around town with very much stop and go driving and around 20.5 highway. I did not check the mileage on the Alpha but there is an even more noticalble power gain between it and the 3.7. It is reallystrong although the shift points seem a little off. My suggestion is to drive both for a couple of days if possible and make a decision from there. Your fuel mileage on either will depend a lot on you driving style.My first impression of the Alpha was WOW but after I got my 3.7 back that memory is fading. Since I have had experience with all 3 available engines with the Modson the I-5 that you are doing , I hope my "seat of the pants" input will help.

 

Thanks RKSmith
Dont get me wrong...I LOVE the V-8 power but when I saw the sticker on the window for hyway milage on the 08 and 09 model Alphas and the way the GAS PRICES was going at 4.00 a gallon,,,thats why I chose the 3.7 Inline 5....Someday i thought about DOWN the ROAD installing a TURBO on my Hummer and Id be Very Well Pleased with the HorsePower and NEVEr go to the V-8....Just waiting for them to make a TURBO Kit for the 3.7. They make them for a 3.5 but NOT for the 3.7 yet when i checkec with turbonetics

 

I have had both a 07 with the 3.7 and now a 09 with the 5.3. The 5.3 hasquite a bit more power,very noticeable. The mileage for me doing the same kind of driving is 1.5-2 mpg lower with the 5.3. I like the 5.3 better as it is much,much smoother but never felt that underpowered with the 3.7. Steve

 

I have an 08 Alpha and I get 15 on the highway if i stay below 75. above that it drops to about 12. My friend has an 07 i-5. he gets about 20 on the highway.

if you dont care about gas mileage go with the 8. such a huge difference in power, escpecially when you put an intake on it.

 

I have the I-5 and to be honest, it seems to be plenty of power for playing around. the torgue is good and if your not towing huge things, you should be a happy with the smaller motor. Both are good platforms though.

 

I have an '08 Alpha with 5K miles now, made a trip to Florida and back towing a 10' cargo trailer. My mileage ran from high 12's to 15 mpg, around town it's in the 12-13 area now, more miles on it should help. Heck, I was getting 12 around town with my H2 on 37's, not sure if changing to the H3 was worth it............. Good luck

 

I have the I-5 and my cousin has the V-8. You can tell a little difference but not enough to make me pay the extra money for it. Like familyhummer said, if your not towing something heavy then the I-5 is the way to go! Hope this helps out!

 

Hey, someone mentioned the black cat exhaust. Is this one better then flowmaster? I have the I-5, would changing the exhaust make it sound deeper and better, or will it just sound like one of those stupid tricked out Honda's. I like the rumble deep sound. Also will the onboard computer be effected by the changing exhaust system. I would hate to drive around with the engine light on all the time.