Better gas mileage and performance.

[HotWheelsBurban]

I've noticed a slight increase in mpg and performance with mid grade. Haven't crunched any numbers yet

Haven't checked the mileage yet, but the big truck does run more smoothly with mid grade!

 

[df2x4]

Haven't checked the mileage yet, but the big truck does run more smoothly with mid grade!

Interesting... I had the opposite experience in my '97s (before any tuning). I tried running 91 octane in both of them and got noticeably worse mileage, plus they felt like they were a little down on power for some reason. Granted this wasn't really an apples to apples comparison as the main reason I tried this was to attempt to run ethanol free 91 from a non top tier station. After switching back to top tier 87 octane the MPG and power came back.

Did you fuel up at a top tier certified station? If so that might have something to do with it. I also went up four points in octane vs your two so that could be part of the difference.

 

[PlayingWithTBI]

Did you fuel up at a top tier certified station?

I'll answer this question, FWIU Fry's and Krogers are not Top Tier stations, at least not here in AZ. Maybe Hot Wheels can confirm this in her area...

 

[0xDEADBEEF]

I see the same Kenan Advantage gas truck at every gas station in my town.

 

[0xDEADBEEF]

The only way to really do both at the same time is put your truck on a diet.

 

[L31MaxExpress]

You’re aboit the only person that says that. I’m not saying accelerate at the pace of molasses in January. Rabbit starts as you describe are proven to be worse for gas mileage. Your MOG suffers most at street driving which is where slow smooth acceleration is how you get better mpg.
You’re not locking the tc on streets anyway as you’re not going fast enough at a steady enough speed for long wnoigh time to benefit from the tc lock up.

tc lockup is great for log steady drive at freeway speeds. Accelerating on a freeway on ramp will get you to speed faster but it’s not gonna return better mog.

I have had plenty of stock GM lockup transmissions that lock up at 20ish MPH even under moderate acceleration. My Q-Jet 700r4 as long as it had 4 in/hg or so ported vacuum on the TCC vacuum switch would lock in 2nd and so would my TBI. My 4L80E also locked in 2nd on the stock tuning.

~1/2 throttle acceleration getting the engine up near peak torque is the absolute most fuel efficient way to accelerate. I have tested it in everything I have owned, from a carbureted SBC to a 320 hp Nissan V6. Slow acceleration has not once saved me any fuel and in fact eats more fuel more times than not.

My city driving can be several miles at a time at 35-45 mph and there definitely is enough steady cruising to benifit from TCC lockup.

 

[Pinger]

~1/2 throttle acceleration

What it does is reduce the throttling losses (and enables engagement of higher gears sooner). BMW in the 1980s recommended exactly what you are saying as the most efficient way to accelerate to cruising speed.

 

[L31MaxExpress]

Even this is was filmed at a bit less throttle opening than I usually use to accelerate. It was to make a point for those that seemed to think a ~2,800 rpm converter causes the engine to jump to 2,800 rpm before the truck would actually move. But even this moderate rate of acceleration sips fuel compared to slow acceleration.

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[L31MaxExpress]

What it does is reduce the throttling losses (and enables engagement of higher gears sooner). BMW in the 1980s recommended exactly what you are saying as the most efficient way to accelerate to cruising speed.

Reduces pumping losses and puts the engine where it has the highest volumetric efficiency thus the best brake specific fuel consumption. It goes hand in hand. The stock Vortecs will not dip into power enrichment until you get to 90% and beyond throttle opening. This same reasoning is why I like a little looser torque converter as well. Adds torque multiplication to help get rolling from a stop without the cruising penatly of a deeper gear ratio and gets the engine into the RPM range where it is most efficient and making the most torque more easily. The overly tight low rpm stall speed GM tends to use lugs the engine and causes it to drink fuel.

My G35 Sedan gets the best fuel mileage accelerating with shift points around 3,500-4,000 rpm where it is close to peak torque. The little short stroke, DOHC 3.5HR revs to 7,800 rpm WOT shift points though.

 

[L31MaxExpress]

Interesting... I had the opposite experience in my '97s (before any tuning). I tried running 91 octane in both of them and got noticeably worse mileage, plus they felt like they were a little down on power for some reason. Granted this wasn't really an apples to apples comparison as the main reason I tried this was to attempt to run ethanol free 91 from a non top tier station. After switching back to top tier 87 octane the MPG and power came back.

Did you fuel up at a top tier certified station? If so that might have something to do with it. I also went up four points in octane vs your two so that could be part of the difference.

My van OEM stock sucked on 87 octane and had audible spark knock from 12,000 miles on the odometer back in 1998 when we got it. Dad knew spark knock, pinging was bad on an engine and switched to premium. It had way more power and 3-4 mpg better fuel mileage so he always used it. It would pull down 19-21 mpg fairly regularly back before the fuel was 10% ethanol on road trips. I later datalogged it on 87 and it would often pull 8-10° of knock retard on the stock GM tuning. I put a cooler 160F Hypertech thermostat in it which helped to some extent and allowed it to run well on 89 octane in the summer and 87 in winter. For many years Hypertech was the only company to offer a 160F for the vortecs.