Talbot

I have the impression that our E320 Bluetec is getting lower mileage than it really should be getting. for the first 5000 miles, an average of 25 mpg with a pretty reasonable amount of highway miles mixed in there. My wife, the primary driver, doesn't drive it hard at all. A recent test on the interstate with cruise set at 75 averaged about 31.6 over 10 miles (outside temp 74F).

So, since we were eligible for our free tire rotation anyway, I had my wife take it to the dealership and have that issue looked at while it was in. Their diagnostics (hooking up to Star Diag, I'm sure) resulted in no findings, and they showed my wife a new Bluetec where under the sticker it says, your mileage may vary. Can anyone suggest reasons (other than my mileage may vary) as to why we're about 15% low on highway mpg? Tire pressure is perfectly set according to the sticker on the fuel filler door, BTW.

Talbot

gdavis808

I'm not a diesel owner (thinking of purchasing the E320 Blutec) but I was reading a Car and Driver review of the E320 Bluetec. From their test drive from NY to Michigan, they averaged 34 mpg. The article is on their website and I would think you should get the same.

JRAMGV8

The engine is still new for 5K, if you ask me. Give a some more time for the engine to break in and it should range in the 30s. but its good that you have it looked at it

harkgar

3,800 pounds curb weight. Then there are the 4 filters. One pre-cat followed by a cat, a particulate filter and another cat and 2 mufflers so the exhaust gases have to be pushed through 6 chambers before exiting.

You have the 7-G which should make up some of the mileage.

I read somewhere too that the Bluetec exhaust system needs to have occasional bursts of excess diesel injected so that the noxious gases can be burned off within the system. Presumably this process will consume more diesel fuel.

I am getting anything from 23 mpg to 29 mpg in mixed driving but I drive fast. This mileage is great compared with my sold E55, 13 mpg to 19 mpg. Even my stick Honda 4 banger does only 26 mpg. The diesel has just over 7,000 miles and the Honda 1,800 miles and I expect more later.

Talbot

It is one hell of a car, and I give it my highest reccomendation.

Talbot

While I agree with all of that, it IS a diesel and I've talked to at least one other person who gets better mileage. So, if it wasn't rated for what it is rated for, your points above would have more merit. It isn't like I'm expecting some kind of out-of-line mileage like that from a gasser. Really, I'm about 15% shy - especially on the highway test. It is somewhat interesting that 15% is pretty close to the ratio of 5 to 6 cylendars, too.

harkgar

Both the Bluetec and CDi are 6 cylinders. The Bluetec a V-6 and the latter straight 6.

I read also the European models had a straight 6 paired off with a 7-G.

Alan Smithee

No, but the Europeans had the V6 with 7G a year or two earlier, and it was called an E320 CDI at the same time the I6 and 5-speed auto was sold here as an E320 CDI.

Talbot

Sorry, I didn't make my point on the 5/6 cyls clear. What I was trying to say is that 15% is about the same difference in cyls if only 5 of the 6 were in play.

actual mileage / expected mileage ~ 5 / 6.

DslBnz

I must admit I do not know how the new system works but...

In 1987, all Mercedes diesels were fitted with particulate traps. Very similar to the E320 Bluetec, without the diesel injection phase.

Fuel economy was 20% less on average than those that did not sport the trap (1986 federal models) and made do with just the EGR system. The restriction only robbed output by 5 hp.

lxl_Jeffro_lxl

1999 E300 TurboDiesel
What would happen if I did a 3'' exhaust system straight from the turbo to the rear bumper, w/a H-pipe, so I can have dual exhaust without the restrictions of all the filters, except possibly a cat or muffler... Please put your input in.

harkgar

I am all for blowing thick black smoke when there is no check engine light!

harkgar

Go to tdiclub.com and find the article on "mufflerectomy" and see what you think.

harkgar

If you are right the 5 horses are free.

More mpg too?

Nevada Jack

This could be the problem?

Talbot

Well, maybe... but... I've talked to at least one other Bluetec owner and his overall mileage is much higher. His overall average is about 29, and with cruise set at 75 on relatively flat interstate he gets around 38 mpg. Ours is 31-32. That's a pretty big difference in an apples-apples comparison.

Alan Smithee

Unless you are comparing two cars on the same day with the same load and same climate conditions on the same road with the same driver...it isn't apples-to-apples. Plus, a true MPG figure must be a two way average to offset wind, elevation changes, etc., and you can't rely on the trip computer.

Your mileage sounds reasonable...don't sweat it.

dtrentr

My Bluetec has about 4K, and I get 33 on the hwy, 27 in town running ULSD B-5 blend if I keep my foot out of it. From 70 to 90 this car has no equal.

erh7771

When you get time fill her up at Shell and and do a couple of WOTs on the highway. After that cruise at 65 till you get to 300, fill another tank and check the millage after a week or two (or 3 hopefully) of note going over 3500 rpm.

daduca

Find a flat highway on a calm day (low wind). Set the cruise control at 65mph and press the trip reset button. See what your average is after about 10 miles. I'll bet it will be close to 37mpg.

lxl_Jeffro_lxl

Haven't found the article yet....I'll keep looking

harkgar

This is an old article I read a while back with a couple of photos showing how the muffler was cut off to allow the turbo to spool up faster. There are a couple of interesting points:

1) the author claimed no increase of power but merely quicker turbo cut-in response time with the cut in exhaust restriction.

2) the turbo acts as a muffler to cut down on engine noise so removal of the muffler does not increase noise level noticeably.

It was a neat job and the exhaust system looks stock.

Ashkan's C43

Where were these traps located? Were they through the exhaust system? What would the mpg be on the trapless cars?

DslBnz

The trap oxidizer should be very obvious if equipped. It is a gigantic "coffee can"-esque apparatus located slightly ahead of the double firewall on the passenger side, behind the turbocharger.

MPG ranged about 21 - 22 mpg/city - highway with the trap in place...Not quite ideal for a diesel car today, but efficient for its time.

There's no need to worry now. Its a non-issue. Dealer serviced cars had the oxidation catalyst replaced with the trap oxidizer after issuing a service campaign, free of charge. The California SDL's will achieve the same mileage as the Federal versions so long as the trap is discarded. And if it has not been done, Mercedes will perform this service for any '86 - '87 diesel, any mileage, any condition, to this very day. So any SDL will perform equally for any year in regards to performance and economy.

BTW, last tank I achieved 31 mpg out of my 350SD (Yes, filled on a level surface no diesel foam, end of the filler neck each time). A 350SD with the same engine as the 300SDL 65% city 35% highway. I'm a proud man. Need to keep your foot out of it at a dead stop, though. You're mileage will suffer tremendously. Especially with no ALDA.

Untertürkheim

Sounds low, but then again, you're still in the break in period. Also, do you keep the climate control on or off, or on economy?