Impressed by 455 mpg.
October 31st, 2016, 07:07 AM
#42
Registered User
Join Date: May 2009
Posts: 1,452
When I drove to the Olds nationals last year I calculated roughly 16-17 mpg on the highway with my C headed 455 as well, not too shabby for a bbo with a 3 speed trans and 3.08 gears. Of course it doesn't have a wild cam and it has stock intake and exhaust manifolds. I started to use the argument that my carb fed Olds was better than most SUV's when criticized about fuel efficiency. Of course street driving is a different story 
It actually gets better gas milage than my stock 72 350 daily driver (11mpg street, 15 hwy) with 2.14 gears and a three speed trans.
It actually gets better gas milage than my stock 72 350 daily driver (11mpg street, 15 hwy) with 2.14 gears and a three speed trans.
What the hell am I doing with a 350!?
October 31st, 2016, 07:15 AM
#43
Registered User
Join Date: Sep 2010
Location: Indianapolis
Posts: 4,848
A few years ago I took my Vista Cruiser to the Oldsmobile homecoming in Lansing with my wife & I & another guy with the back loaded with parts to sell & with a moderate 455, th200 4r & a 4.10 posi I got about 12-13 mpg at 70-80 mph. I thought that was reasonable for a vehicle weighing about 5,000 lbs.
October 31st, 2016, 12:06 PM
#44
Registered User
Join Date: Jul 2013
Location: Mo-Ray-Al, K-Bec.
Posts: 1,815
Am I the only one who saw the thread title and thought "No way in hell are you getting 455mpg"?
Calculating mileage ... Fill the tank until the pump clicks off automatically. Don't round up. Note odo reading on receipt. Repeat as needed. Enter odo reading, liters purchased, and dollars spent into an Excel spread sheet. You will see swiftly any variations, which will be averaged out over the months. I try my best to fill at the same station, and from the same pump. If not, doesn't matter .. it averages. This is the method I used to discover that my mileage per liter improves if I use non-ethanol super over 10% regular. Improves enough to eat the difference in price (mileage/dollar)... particularly in winter.
Calculating mileage ... Fill the tank until the pump clicks off automatically. Don't round up. Note odo reading on receipt. Repeat as needed. Enter odo reading, liters purchased, and dollars spent into an Excel spread sheet. You will see swiftly any variations, which will be averaged out over the months. I try my best to fill at the same station, and from the same pump. If not, doesn't matter .. it averages. This is the method I used to discover that my mileage per liter improves if I use non-ethanol super over 10% regular. Improves enough to eat the difference in price (mileage/dollar)... particularly in winter.
November 1st, 2016, 03:11 AM
#45
If set up for economy, instead of performance, good mileage is possible.
Back in the late 80's, a friend and I drove to car shows in NY, Virginia, Ohio, from NJ, with our customs. I had my 55 Olds, stock driveline, but with a 3 x 2 set-up on it (J-2 carbs). He had a 56 Mercury, sitting on a 72 Grand Prix chassis, with a 455 Olds engine, TH400. On the highway we were both getting a hair over 20 MPG, driving a bit over the speed limit, but not racing, or showing off. We did many, many miles like that.
Back in the late 80's, a friend and I drove to car shows in NY, Virginia, Ohio, from NJ, with our customs. I had my 55 Olds, stock driveline, but with a 3 x 2 set-up on it (J-2 carbs). He had a 56 Mercury, sitting on a 72 Grand Prix chassis, with a 455 Olds engine, TH400. On the highway we were both getting a hair over 20 MPG, driving a bit over the speed limit, but not racing, or showing off. We did many, many miles like that.
March 4th, 2021, 07:07 AM
#47
Registered User
Join Date: Mar 2021
Posts: 1
Oldsmobile did some work on this back in 1967 with the Turnpike Cruiser option only available on 2 door cutlass S models. It was a total package that also addressed the suspension. All these had the 442 suspension with Boxed control arms, front and rear sway bars, HD shocks and springs.
Tall gearing was the key to fuel economy being that engine friction robs power so lower RPM reduces engine friction and increases fuel economy. The Rear end gearing I believe was 2.56:1. With tall gearing like that, you needed torque for around town so they detuned the 4" bore 400ci V8 from the 442, keeping the same big valve heads and 10.5:1 compression ratio but then installed a specially calibrated 2 bbl carb with the Climate Combustion Control system ( a fancy name for a valve to preheat engine intake air to maintain 100F to allow for leaner jetting, same as all Oldsmobiles had in 1968), and a special short duration ( 250 deg intake, 264 deg exhaust) low over lap ( 36 degrees) and low lift .435" cam. And it came with a true dual exhaust system.
Output ratings for this combination at that time was 300HP @ 4,600RPM with 425Ft Lbs at 2600 RPM.
This combined with the switch pitch ( last year for this) Turbo 400 which essentially offered 2 different stall speeds, allowed the car to work well in city driving but get way better fuel economy than the typical 330V8 with the Super Turbine 300.
Car Life magazine testing reported 19.26mpg @ 60mph and 17.22mph@70mph. Very respectable for those times and considering it could carry 6 people and all their luggage, not bad by today's standards as well.
But fuel was $.29 per gallon back then and fuel economy was not a big selling feature so it was not popular. These are rare cars to be sure but those figures could be improved even further with modern engine oil, a roller cam swap with similar specs, a cross over tube after the exhaust manifolds ( improves low end torque), a K&N air filter in the stock special air filter housing, and perhaps a Petronix electronic ignition. Modern radials wouldn't hurt either as would a set of headers.
It looks possible that with modern revisions, 20mpg at 70mph could be reached.
Tall gearing was the key to fuel economy being that engine friction robs power so lower RPM reduces engine friction and increases fuel economy. The Rear end gearing I believe was 2.56:1. With tall gearing like that, you needed torque for around town so they detuned the 4" bore 400ci V8 from the 442, keeping the same big valve heads and 10.5:1 compression ratio but then installed a specially calibrated 2 bbl carb with the Climate Combustion Control system ( a fancy name for a valve to preheat engine intake air to maintain 100F to allow for leaner jetting, same as all Oldsmobiles had in 1968), and a special short duration ( 250 deg intake, 264 deg exhaust) low over lap ( 36 degrees) and low lift .435" cam. And it came with a true dual exhaust system.
Output ratings for this combination at that time was 300HP @ 4,600RPM with 425Ft Lbs at 2600 RPM.
This combined with the switch pitch ( last year for this) Turbo 400 which essentially offered 2 different stall speeds, allowed the car to work well in city driving but get way better fuel economy than the typical 330V8 with the Super Turbine 300.
Car Life magazine testing reported 19.26mpg @ 60mph and 17.22mph@70mph. Very respectable for those times and considering it could carry 6 people and all their luggage, not bad by today's standards as well.
But fuel was $.29 per gallon back then and fuel economy was not a big selling feature so it was not popular. These are rare cars to be sure but those figures could be improved even further with modern engine oil, a roller cam swap with similar specs, a cross over tube after the exhaust manifolds ( improves low end torque), a K&N air filter in the stock special air filter housing, and perhaps a Petronix electronic ignition. Modern radials wouldn't hurt either as would a set of headers.
It looks possible that with modern revisions, 20mpg at 70mph could be reached.
March 4th, 2021, 07:11 AM
#48
Registered User
Join Date: Aug 2012
Location: Colorado Springs Colorado/Thousand Oaks Ca
Posts: 1,722
It's possible. Over time that I have checked mine I got right around 20 @ 60-65 sustained on highway, trying to be good. Around town, not sure but with a majority around town combined w/ maybe one or two moderate trips on highway it will be appx 15mpg. I have to admit that I rarely get that mileage on the highway because I'm typically traveling @ 80 or a tad higher, it's just where the car is happy if traffic conditions allow. Engine turns 2300 @ 70mph. This would be on E10 warm weather blend fuel.
When we drive to drag strip we go appx 240 miles, get a good mix of in town, secondary highway, short stint on Mass Pike and 8-10 drag runs, returning w/ a hair under a quarter tank left. My speedo shows 1mph over the radar speed signs so it is pretty accurate, If I could go all highway & lock converter mileage would increase, car doesn't like to be locked up in OD under 50-55 mph.
None of this is laboratory tested but is a reasonably accurate indicator.
Granted, it is 434 ci not 455 but close. Considering 3.90 w/ appx 26.5" tires that's pretty good, largely due to OD, Qjet & tuned for drivability.
Red car w/ lightly warmed over 350, 3.08, 200-4R turns about 1800 @ 70 but I don't know what it gets for mileage. It's my kid's year round DD & I have never driven a tank of fuel through it but it seems easy on gas until you get to the infamous last quarter of a tank or stick your foot in it more than a few times.
When we drive to drag strip we go appx 240 miles, get a good mix of in town, secondary highway, short stint on Mass Pike and 8-10 drag runs, returning w/ a hair under a quarter tank left. My speedo shows 1mph over the radar speed signs so it is pretty accurate, If I could go all highway & lock converter mileage would increase, car doesn't like to be locked up in OD under 50-55 mph.
None of this is laboratory tested but is a reasonably accurate indicator.
Granted, it is 434 ci not 455 but close. Considering 3.90 w/ appx 26.5" tires that's pretty good, largely due to OD, Qjet & tuned for drivability.
Red car w/ lightly warmed over 350, 3.08, 200-4R turns about 1800 @ 70 but I don't know what it gets for mileage. It's my kid's year round DD & I have never driven a tank of fuel through it but it seems easy on gas until you get to the infamous last quarter of a tank or stick your foot in it more than a few times.
March 4th, 2021, 03:54 PM
#49
Gary
Join Date: Feb 2014
Location: Gillespie County Texas
Posts: 2,218
I've had two 455s. The one in my 442 with 3.23 gears got 15 mpg highway. The one in my Vista Cruiser got 14.5 mpg highway with 2.56 gears.
I've not tested the Vista since I added the double overdrive transmission which gave a rear gear equivalent to 2.05.
Gary
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