As many already know, my dad has a '97 Park Avenue Ultra. He states that he improves his fuel mileage by getting to the speed limit as quickly as possible. Of course being supercharged 35 comes pretty easily to him. He also states that when my mom drives the car <who carries a pretty light foot> his avg mpg drop by about 2. Of course this seems beneficial only to those who can reach the speedlimit quickly and effortless at the same time <i.e. NOT the L27>.

Thoughts?

I guess I see the reasoning behind it, but maybe he is wrong?

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~Randall~


1993 Buick Park Avenue - 197k - Some odds and ends done - Simply won't die
1994 Buick Regal - 78k - Bone stock - Always ready for a good kicking
1990 Oldsmobile 88 - Gone to a better place

Well, I know that when I get to the speed limit as quick as possible ( WOT ) with either the '93 or the '03 I can about watch the gas gauge move. I would assume that he is talking about getting there quick, but maybe only using 1/4 - 1/2 throttle. Any more then that and it will drink the fuel... big time.

Driving the '93 like I normally do, very heavy foot, I get about 280 out of a full tank. I have gone through a few tanks as well driving it very easy and can get about 400 to a tank.


He must have an all highway commute? Other then that, 35 is going to be dang near impossible to hit. Most everyone here seems to get around 22 - 25 with mixed driving and only average in the 30s with longer highway trips.

As far as a two MPG decrease, unless they each drive it for a full tank at a time, that also is going to be about impossible to really tell if it is her driving style vs. his. If he drives for five full tanks and gets X mpg, then she drives for a tank and gets two less mpg, it could be different outside temps, traffic conditions, city / highway mix, hitting red or green lights in the city, etc... There are so many factors that can contribute to a small increase or decrease in mpg that it will be very hard to tell what exactly the cause is if she only drives it once in a while.

I think it all depends on what his idea of "getting to speed as quickly as possible" is.


Also, the L27, L36, and L67 should all get about the same city and highway mileage if they are in good tune.

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Ryan

2003 Bonneville SSEi - The Black Mirror SOLD!
2002 Bonneville SE - The Mutt Complete 2004 SLE interior, drivetrain, and body harness swap, ECC swap, HUD swap, black GXP wheels, GXP headlights and tinted tails - SOLD
2003 BMW 540i M Sport, 2001 BMW X5 4.4i, 2010 GMC Acadia, 2017 Grand Design Imagine 3150BH
1982 Cutlass Supreme - The fun one

35 MPH, sorry

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~Randall~


1993 Buick Park Avenue - 197k - Some odds and ends done - Simply won't die
1994 Buick Regal - 78k - Bone stock - Always ready for a good kicking
1990 Oldsmobile 88 - Gone to a better place

If you accelerate fast, there is a theory that the inefficiencies of the motor are minimized due to the fact that it is under load for a shorter time, giving better fuel economy. One thing i learned in my Ei (and will hopefully learn in the near future) is that getting into boost drops fuel economy really quickly. I accelerated so hard that the Instant Econ Read 0 till i let off, LOL.

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Bye Bye:

RIP sandrock

there is a balance somewhere in between. you dont want to accelerate so slowly that you are under load for a long time, with no TCC lockup, but you also want to try to keep RPMS low. the basic rule of high RPMS = bad mileage still applies.

If you're moving forward...do it as slowly as possible. That actually doesn't take that long with the L27...its low end torque gets you up to speed pretty quickly..but I usually do about 1/4-1/2 throttle when in town or something like that, rarely more. The exception is getting onto the highway where I used to live up in Wisconsin, it was a direct turn right on to a 65 MPH expressway with a constant traffic flow, but still only took about 3/4 throttle to get me up to 70 without much issue....I averaged about 22-23 for city/highway, and 29-32 for highway w/ cruise engaged. 22-23 actually amazed me with my pretty heavy foot every once in a while...getting on a twisty on-ramp or needing to get up to speed especially quick.

With my mother driving it, who has a generally light foot and consciously tries to keep the shifts below 2000 RPM while accelerating, has returned about a 26-27 mpg average on several tanks of mixed driving, and since she tends to drive the speed limit at around 65 on the highway, usually gets about 34.

I'd be very surprised if it was actually that a mid throttle, getting you to speed quicker actually saves fuel, or if the higher of the low mpg average with accelerating slowly returns higher numbers.

A special wide parameter scantool, one that displays actual units of fuel consumed would help quite a bit in finding this.

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John
Now: '15 Toyota Prius III | 134 hp 2ZR-FXE | Silver | 36k
Now: '03 Honda CR-V AWD | Slow 4-Cylinder | Dirt | 180k
Then: '07 Ford Fusion SEL | 221hp Gen I VVT Duratec 3.0 V6 | Tungsten Silver | 150k
Then: '99 Toyota Avalon XL | 200hp 1MZ-FE 3.0 V6 | Diamond White | 189k | Sold: July 2015
Then: '11 Ford Fusion SEL | 240hp Gen II VVT Duratec 3.0 V6 | Ingot Silver | 84k | Totaled: Oct 23 '14 (Rear-Ended)
Then: '96 Buick Park Avenue Ultra | 240hp Series II L67 | Medium Dark Lichen | Bought: JAN 11 @ 135k | Accident: FEB 3 '12 | Crushed: MAR 1 '13 @ 153K
Then: '98 Pontiac Bonneville SSE | 205hp Series II 3800 L36 | Topaz Firemist | Bought: NOV '09 @ 74k | Accident: MAY 28 '10 | Crushed: MAR 15 '11 @ 84k
Then: '93 Pontiac Bonneville SE | 170hp Series I 3800 L27 | Dark Yellow Green | Bought: JULY '07 @ 92k | Sold: JULY '12 @ 118k
Then: '89 Pontiac Bonneville LE | 165hp 3800 LN3 | Medium Garnet Red | Bought: JAN '05 @ 117k | Sold: SEP 30 '07 @ 152k

The theory states that faster accelerating to speed means less fuel ultimately being used since you can use much less throttle to maintain the speed you already have, vs. using fuel to constantly slowly accelerate the car.

The problem with the first is that you have to be really specific to cut off at the speed you want and not overshoot, making you use the brakes in the worst case. And you need to be more cognizant of lights ahead of you. No sense in blasting up to 30 mph if you will just spend the next minute idling at the light. In that case 20-25 mph will be better since you may be going slowly enough to catch the light.

_________________
2012 Chevrolet Cruze Eco - Current car

1999 Buick LeSabre Custom - Former car

Learn from the mistakes of others, that way when you mess up you can do so in new and interesting ways.

I just gun it up to 60 and pedal it up to 65, it really has made very little difference in my fuel economy (less than .25 mpg, average) and it is so hard to calculate, because of weather and other driving conditions.

_________________
Bye Bye:

RIP sandrock

For those with scangauges, it can be calculated. IPW will give us the numbers we need to figure it out over time.

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Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

I am not quite a Mechanical Engineer yet, considering I am junior, but from what I have learned about mechanics, it seems that any kind of big acceleration is a "loss" of energy.

When accelerating in my car, I can actually keep the rpms below 2,000 rpms and I always thought that I was being most efficient.

I know efficiency has not do with rpms, but actually the load on the engine. Due to this, I always wondered at a certain speed, what rpm is more efficient? I have come down to conclude that the load on an engine is already calculated into the PCM for shift points, but probably not so much for downshifting. But then I realized that our transmission downshift via the throttle cable hitting at a certain throttle position. So, the pcm only controls the rpms when I speed up?

This all started because I live in an area with a lot of hills. I am constantly wondering if it's better to let OD with the TCC locked out continue to keep the rpms low and drag through OD at 1200-1200 rpms, or drop it into "3" and downshift on a hill say to 2300 rpms instead.

I guess the only way to know would be to find out the actual load on the car at any given moment.

I might have not been clear, if you have any questions about my random talking, feel free to ask.

Also, please seize the moment and correct anything I may have stated incorrectly.

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Current: '12 Audi S4 Quattro Prestige 6MT

Previous: '06 Audi S4 Quattro 6MT (for sale!)
'06 Chevy Cobalt SS, Stage II: 2.0L Supercharged, 16psi boost, G85 Package; Recaro Racing Seats, Limited Slip Differential, 5 Speed Manual
'00 Pontiac Bonneville SE ( 4 years, 197,000 miles)
'99 Dodge Intrepid ES (1 year, 2 engines)
'95 Chevy Lumina (2 years, 164,000 miles)

There are alot of variables, including slip rpm's for the TC. That's wasted energy. But from a basic standpoint, which is how much fuel is consumed, a simple calculation based on injector pulse-width in both conditions and the amount of time under which IPW/throttle setting would tell us some info, perhaps enough to draw an obvious conclusion without even having to take into account the load factors, tc slip, etc.

_________________

Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

I should add some information I gathered yesterday.

According to my truck's DIC, when I accelerated to speed (45 mph in these tests) up to 3000 RPMs, or, with a noticable inertia, I averaged approximately 14.5 MPG for city driving over about 25 accelerations.

However, when I made a conscious effort to keep the shift points at 2000 RPM or below (which I must admit, really isn't that hard to do.) I averaged approximately 16.3 MPG. The basic idea behind this was that even when accelerating very lightly, the engine was delivering enough power at that RPM to make the trip to speed very short...probably only 10 seconds or so.

I'll be sticking with the latter number.

_________________
John
Now: '15 Toyota Prius III | 134 hp 2ZR-FXE | Silver | 36k
Now: '03 Honda CR-V AWD | Slow 4-Cylinder | Dirt | 180k
Then: '07 Ford Fusion SEL | 221hp Gen I VVT Duratec 3.0 V6 | Tungsten Silver | 150k
Then: '99 Toyota Avalon XL | 200hp 1MZ-FE 3.0 V6 | Diamond White | 189k | Sold: July 2015
Then: '11 Ford Fusion SEL | 240hp Gen II VVT Duratec 3.0 V6 | Ingot Silver | 84k | Totaled: Oct 23 '14 (Rear-Ended)
Then: '96 Buick Park Avenue Ultra | 240hp Series II L67 | Medium Dark Lichen | Bought: JAN 11 @ 135k | Accident: FEB 3 '12 | Crushed: MAR 1 '13 @ 153K
Then: '98 Pontiac Bonneville SSE | 205hp Series II 3800 L36 | Topaz Firemist | Bought: NOV '09 @ 74k | Accident: MAY 28 '10 | Crushed: MAR 15 '11 @ 84k
Then: '93 Pontiac Bonneville SE | 170hp Series I 3800 L27 | Dark Yellow Green | Bought: JULY '07 @ 92k | Sold: JULY '12 @ 118k
Then: '89 Pontiac Bonneville LE | 165hp 3800 LN3 | Medium Garnet Red | Bought: JAN '05 @ 117k | Sold: SEP 30 '07 @ 152k

Getting into boost is not the most efficient way of getting around normally. I get much better mileage accelerating at a normal pace below 2k in my car, Accelerating faster, say heavy foot + boost below 3k, uses much more gas, even if short shifting. I've heard claims of flat foot on accelerator + very short shifting is supposed to be beneficial in cars with more gears + turbos like mine, but i've seen quite the opposite.

Try to accelerate on down slopes as much as possible too. If there's a "bump" in the road, slow down the accleration going up it, and then give it more on the way down.

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Jason Z - Exposed Autos

2001 BMW 330i - Titanium Silver - Sport Package - 3 Pedals - Koni Yellow/H&R Sport
2006 Volkswagen GTI - (gone) Tornado Red - DSG, Stage II~280hp/325tq
1993 Pontiac Bonneville - (gone) Purple Pearl H4U/SLE. Loud

This does not appear to apply to my GXP. It gives the best mileage when driven very gently. With great effort I can get 20mpg in town. Yet if just once I give it say 1/3 throttle up to 40, the average mileage will drop below 20, and it takes several miles of easy driving to get it back up to 20 again. That is even if I don't have to apply the brakes soon after.

Certainly it is possible to go too slow for max mpg, but in my GXP, that would be a snails pace based on what I've observed on the DIC.

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2005 GXP Silver, Gutted Airbox, K&N filter, 14.61 @ 94.31 mph.
1987 t-bird 2.3 turbo, stock motor with home-ported head, big turbo, big exhaust, alky injection, a bunch of other little stuff, 13.65 @ 102 on radials.

Maybe mom rides the brakes?

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2004 Buick Lesabre Limited, Gran Touring
Bone Stock

1998 Buick Lesabre Limited, Gran Touring
Retired

Maybe Mom stops for red lights.

Who you tryin to kid? Mom has a heavy foot!

Keep the engine at the lowest rpm possible and lug it without downshifting.

Don't stop the car or use the brakes at all.

Let your speed drop if any hills. Keep the lock-up TC locked.
I hate doing that.....have to constantly let up on the pedal to disengage it. We have a lot of hills here. Probably why I don't get more than 15 mpg in town.

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2000 SSEi - SilverBullet - 78,000 kms, 4" "straight shot" custom headlight ram air inlet, TOGs, 1.9's, Lsd, 2.9-3.4"MPS 10-15 psi, Ported GenV, EGR eliminated, OR pushrods, oil volume kit, trani cooler & shift kit, Titanium retainers, 90 lb springs, 160 Stat, 42# injectors, Fuel pump voltage increase, Wideband O2, 3" to dual 2 1/2" Magnaflows, Snow Meth/water injection, after SC temp gauge, 255/50WR17, timing commander set 15-18*@WOT, 2 speed Fan over-ride, disabled DRL, Solid motor mount, Meziere Electric water pump, adjustable fuel pressure regulator, Drilled & slotted rotors/ceramics, GXP sway bars and STB, Upgraded and rebuilt transmission with ZZP 2500 rpm stall TC, Pioneer Bluetooth stereo with sub and 800 W amps, PB 13.5 quarter, (April 2014 car of the month)

This is key. When cruising up and down highway 401 every day (it's north america's busiest highway), traffic speed is always variable from 90 to 120 km/h (55 to 75mph), ideally I'll cruise at about 105km/h (65mph). I always keep sufficient distance from the car in front of me and eyeing the boost gauge helps to keep minimum throttle with a locked TC.

In the city, another trick is to leave some distance from the car in front and start creeping forward early. I don't hit the throttle until about 2 or 3 km/h on the HUD... this gets you over the hump of the inertia involved when you're at a dead stop. This was much easier to do with the super-short geared Civic, which would push forward really quick off idle.

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Jerry /// Past: 95 SSEi (June 2010 COTM) -- 04 GXP (July 2011 COTM)
91 Honda Civic Wagon DX 2WD (fuelly) -- 208,000km -- 92hp -- Autocross Warrior
09 Lexus LS460 AWD -- 94,000km -- Daily Driver
09 White Hot G8 GT -- 155,000km (fuelly) -- LS3 Cam -- GM LS3 CNC Ported Heads -- Kooks 1 3/4" Long Tube Headers -- Solo Catback Midsection -- Hooker Maxflow Mufflers -- Pat G Tune -- Rotofab Intake -- Tein S-Tech Springs -- GXP FE3 Dampers -- BMR Subframe Cradle Inserts -- BMR Subframe Connectors -- Forgestar F14 Gold 18x9 +40 -- Michelin Pilot Super Sport 245/45/18 -- Maverick Man Carbon Fiber Spoiler