1985 300D Calif version Milage - PeachParts Mercedes-Benz Forum

Bill3888 · #1 11-06-2002, 01:47 AM

Hi - got a great running car but the milage won't get above 20mpg! Anyone out there getting about the same or better? Car runs so nice I'm sure there are no major problems with it except for the typical vacuum leaks in the air control sysytem and doors - Tried blocking the EGR and Bypass on the turbo but got identical milage - Any Idea's or is this normal??

1stimer · #2 11-06-2002, 02:00 AM

I am definitely a newbie, and don't know if this would cause bad mileage, but even it didnt it wouldn't hurt to check out. I feel weird giving advice and someone please correct me if I'm wrong, but I think the 85's from california had a trap oxidizer that can still be fixed/repaired under recall...found this thread and i'm sure there is more if you search for trap oxidizer or 1985 or something to that effect. Trap Oxidizer

lrg · #3 11-06-2002, 02:26 AM

The oxidizer shouldn't affect your mileage much, it's some of the other stuff that California required that can but it sounds like you've taken care of most of it. I have an '85 Calif. wagon that gets 25-26 highway and 21-22 city (if my wife drives) and 18-20 city (if I drive). If I slow down I can get better mileage but I do like making that turbo earn its keep. Lugging all that steel up and down hills in San Francisco definitely takes extra fuel (and brakes). Even so the Calif version does loose a 1-2 mpg compared to the 49 state cars.

adamb · #4 11-06-2002, 05:47 AM

Hello, I as well have a 1985 300D-T and it gets about 23 mpg. Every once in a while I might get 26 out of it, but only when I am really gentle on it, and I consider that mileage pretty good considering the published mileage is 21 city 22 highway.
I bought the car 18 months ago with 132K on it, and it now has 162K and the mileage and reliability have been very consistent. I got the trap replaced for free, as you should, did what you did with the EGR and Bypass (which was leaking causing all sorts of vacuum related problems) and bypassed the electronic overboost valve on the firewall beside the brake power booster. I also got rid of all the assorted vacuum related valves that were controlling the EGR and Bypass, which were locvated beside the power steering pump, and that cleaned up the engine area pretty good.
I understand your concern, as I bought my diesel thinking it would get about thirty mpg, but only after investigation realized the best it would do is what I mentioned. I do all my own work and still have put over 4,000 into this car in parts I have bought on-line (all-OEM stuff). I try to resist the urge to sell it to get a 190D, but that fuel mileage for a car I want to keep wouls sure add up over time.
Good Luck, Adam

Joe Blowe · #5 11-06-2002, 12:04 PM

Bill3888,

In my opinion, the first thing you should be checking is your odometer. Take your car out on the highway for a long run, and use the milage markers for a comparison against your odometer/trip odometer.

Mine was off by about 17%, thus making my fuel economy look like crap...

Dcraig · #6 11-06-2002, 12:47 PM

I also have a California '85 300CD and I get about 26-28 combined City/Hwy. If I was able to keep it at the speed limit, I'm sure it would go up, but love it when I pass a gas car at 85mph.

I'm sure if you've put that much into the car you've changed the air filter. Fuel timing?

Craig

GregS · #7 11-06-2002, 01:14 PM

Sounds about right to me. I have an '84 California-version 300D and I consistently get 23mpg. Oddly, it doesn't matter at all whether I drive city or highway (o.k., on a very long trip (300+ miles) I might get 24mpg!). The one thing I have noticed is my car spins at a relatively high rpm, making me think the california models had a lower rear-end ratio. I drove an '84 SD once and it was only spinning around 2800rpm at 65 - my car spins around 3200rpm. Higher rpm will surely make the car use more fuel. Why MB would want the car to scream along on the highway like that I don't know, but I have often thought of looking into swapping the rear differential. Supposedly the rear end of '85s have a lower rear end, which makes for better cruising and mpg.

Greg

adamb · #8 11-06-2002, 02:40 PM

Good point about testing your odometer. I pretty much always use my Garmin 196 GPS and have found my car to be off by about 6%, so I take that into account when calculating the fuel mileage. One other option for you would be to go with a taller tire maybe - anyone have any experience doing this?

Thanks, Adam Bush

curston · #9 11-06-2002, 10:58 PM

I also have an '85 300D California version. It has 106,000 mi on the clock. It is in great shape, and gets from 21 to 24 miles to the gallon. The original window sales sticker came with the car and states the expected mileage as 21 in town and 22 on the highway. It dosn't seem to matter much how it is driven. I have taken 400 mile trips and held it at 68 to 70 MPH going and 80 or so on the return trip. There was less than 2 MPG difference, as I recall.

Bill3888 · #10 11-06-2002, 11:02 PM

Hi - Thanks for all the feedback - Trap oxidizer has been removed - I'll check the odometer - just assumed it to be fairly accurate - Gets 20 - 21 on mixed freeway/city and I too use the turbo - have noticed the high rpm (actually a little annoying since I like to cruise around 70) about 3250 on the rpm - Car has excellent response when warm - turbo comes om much faster then others I've driven (85 fed and 83) I'm begging to think the Calif version won't be good for much over the twenty - I plan to set valves this weekend and find the vacuum leaks too - Does have the recommended tires ( 14s) - after hearing reports about the EGR and Bypass I was actually surprised the mileage didn't improve at all? Once again thanks for all the suggestions !!

Dcraig · #11 11-07-2002, 01:57 AM

I was told my my indie mechanic (old German guy that worked for MB in Germany) that disabling those things doesn't make a big difference on the CA version.

He told me that after looking at my engine and asking what the screws were in the vacuum lines.

Craig

GregS · #12 11-07-2002, 09:21 AM

I too read on this page that disconnecting the EGR on the Cali-versions doesn't have any affect. People with other cars claim they get improved fuel economy and quicker accelerator response. My car is already pretty quick, so I don't care about acceleration, but I feel better knowing that exhaust soot isn't being thrown back into the intake manifold. Unplug that EGR!

Greg
'84 300D, 168K

gsxr · #13 11-07-2002, 03:26 PM

Yep, your MPG is a bit low. There are a zillion things that can cause it. As mentioned, check your odometer, they are notorious for intermittent operation that you may never notice. Also the 1985 cars (Fed & CA) are very different than the older ones - different tranny, torque converter, vacuum system, rear end ratio, etc, etc. But they should still get decent mileage. Check all the basic stuff - tire pressures (32+), brakes dragging, alignment, air filter, fuel filters, IP timing, valve adjustment (every 15kmi), timing chain stretch, engine temp (80-100C), etc, etc. One other thing - if you live in CA you get 10-20% lower MPG than everyone else. You can thank CARB and the EPA for shoving lower-BTU fuel into your tanks. All 4 of my cars get *significantly* better MPG using non-CA fuel! I have years of records on all the cars in CA, and in the 4 months I've been in Idaho the MPG improvement is amazing (ID, NV, WA, and OR fuel all seem equally good so far.)

FWIW, my 1984 gets crummy MPG too, about 20-22 around town, and 22-24 on the freeway (with good fuel - knock 2mpg off that for CA numbers.) I know numerous other people with 123.133's that get 25 city, 30 highway, which is what these cars SHOULD get when in PERFECT condition. I have tried almost everything in an attempt to cure the poor MPG. The only two things left are the master cylinder (I think the brakes are dragging very slightly), and checking the timing chain stretch. All else has pretty much been eliminated. I'd like to fix both before I sell it just to know what it was! I want to sell it and get a nice 190D instead (I'm spoiled by the 124's and want to unload the frumpy ol' 123!)

:p :p p

Regards,

Alan S · #14 11-07-2002, 06:06 PM

Hi, I've also got an 85 300D, California model, that is kept in pristine shape. All maintenacence is kept up, and I drive all highway, approx. 3000 miles a month! The absolute best I've gotten was 26mpg. It makes little difference between city/highway. However, if I use the A/C, my milage drops to 20-21 mpg. So if your using your a/c and still getting 23 mpg, your doing great!

Bill3888 · #15 11-07-2002, 09:44 PM

Nope - That's without the ac or with it - seems to not matter.