E430 Fuel Economy
28.4 MPG on the freeway, air conditioned at 70 MPH and 98F!
I've logged 9,325 GPS-calibrated miles on my E430 and consumed 463.654 gallons of premium fuel doing it between June 2006 and August 2007.
This averages 20.112 real MPG. I drive mostly locally, with some long freeway travel and some closed-track driver safety training time.
My personal best on a freeway is 30.6 MPG as documented below.
These are calibrated values. The dash computer is reasonably accurate, but that's not where I'm reading these.
For a big, fat, powerful V8 luxury car, this is excellent!
Premium unleaded fuel only.
91 pump octane ((R + M) / 2) minimum.
Excellent! Driven properly, this big Mercedes with a meaty, premium V8 returns the same or better efficiency than a dinkier car or engine. Our dinky Saab 9-3s with 4-cylinder engines get the same or worse mileage!
Today there's no fuel penalty for the power, authority and safety of a modern Mercedes V8.
The V8 is only turning 1,900 RPM at 60 MPH, while it's sixteen (16) spark plugs ensure every picolitre of fuel is completely burned.
The E430 looks like a rounded teardrop. It slides through the air effortlessly.
Open Freeway: 30 MPG
On October 26th, 2006 I averaged 30.6 MPG for two hours driving at 58 MPH at 68F in California's central valley. This is the actual calibrated value, not read from a dashboard computer.
This was with the air conditioning and headlights on, which lower fuel economy.
Fast and Hot
MPG drops with high speed and if the A/C has to work harder.
I got 28.5 MPG on a recent 300 mile trip to Vegas shown above. The computer shows 28.2 MPG, and I got 28.5 MPG (calibrated) by the time I arrived in Vegas and refueled. I calibrated this with my GPS, so it's a real 28.5 MPG, not inflated by a couple of MPG as most other brands of in-car computers do to make you happy.
It was hot out there, up to 98F, so the A/C had to work harder which lowers MPG, as does driving faster. I had the A/C set to 66F; I like it cool.
The computer was off by 0.2 MPG: after filling my tank I actually got 28.5 MPG, likewise, the tank only took 10 gallons, less than half it's capacity.
After a fast run to Vegas from northern San Diego.
I remember the days when we needed Diesels to get to Vegas on a half tank.
I average 20 MPG the way I drive, mostly short, local trips, over the past six thousand miles.
Overall MPG will depend on how much time you spend locally (low MPG) and how much time you spend sliding down a freeway at constant speed (high MPG).
Commuters who drive in traffic or locally will get less, and people who usually drive long, uncluttered freeways will get more.
I get the same mileage from most cars with short local trips and a lot of stopping.
It's not 1974 anymore, thank God. My first car, a 1974 Plymouth Duster with a small slant-six, no options, no air conditioning and manual transmission, got 17 MPG on long trips and 16 MPG locally. It only had 92 HP, a third the power of the E430!
To get real readings you need to know the real distance traveled and the actual amount of fuel consumed.
You must check the calibration of your odometer. Many cars are off by a a percent or two, which can mean as much as 1 MPG when you do your calculations.
I calibrate my odometers against my GPS.
You're at the mercy of the pump's calibration for fuel. I've never noticed any variation anyplace I've refilled my tank: the gallons indicated on the pumps always have agreed with my other calculations.
Thus I apply a calibration factor to my odometer and take the fuel at pump value.
I cover the MPG computer, its calibration and other oddities on its own page here.
The built-in computer reads very low for short trips (20 miles). It is amazingly accurate for long segments (300 miles).
This is because it presumes that you've been driving with very poor efficiency for a few miles before you reset it, so it takes many miles for your better mileage to be reflected on the computer.
I have no idea why Mercedes does this, except that this keeps the reading stable (but low) after reset. Every other computer reads much more variably after being reset, since other computers read the true values immediately after reset. This E430 computer reads a presumed low value after being reset. This is obvious: other cars will read 0.0 or 99.9 MPG when reset, depending on if you're rolling down hill or stopped. The E430 computer usually reads something between 7 and 15 MPG after reset.
Here are the EPA ratings by year:
Fuel economy in real driving depends more on your driving than the EPA ratings. The EPA ratings for all these cars never varied by more than a few MPG from a low of 16 city / 21 highway in 1992 to a high of 19 city / 26 highway in 1998.
Most people in most cars get less MPG in the city and more MPG on the open freeway than the EPA results. EPA test methods have been irrelevant for decades, but they do provide the only easy way to compare cars and models across the years because the tests remain the same.
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