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  #16  
Old 02-07-2008, 10:52 PM
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Check the easy things first - fuel cap

I bought my 300D new in 1983 (over 200K miles) and never had a problem with the fuel cap until a couple of months ago. I noticed a diesel odor and discoloration on the fender. Checked the fuel cap and it felt firm but in reality only one tab was engaged. Reseated and cleaned the car - no problem. Happened again this week. I don't know how much the mileage decreased, but I was clearly pumping diesel on the ground from the return line.

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  #17  
Old 02-07-2008, 11:37 PM
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As promised:

My tires pressures are all within the realm of normal - 30 in the front, 32 in the rear. Air cleaner is nice and clean - no oil is evident on it. My fuel cap absolutely seals positively based on my inspecting it.

I had a look around the IP and the injectors again just to be sure, and everything is nice and dry as a bone.
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  #18  
Old 02-07-2008, 11:43 PM
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Quote:
Originally Posted by Cr from Texas View Post
I noticed a diesel odor
Good point; after the commute do a sniff test and see if you get a whiff of Diesel Fuel (including under the hood). I had a small fuel leak at the filter and the first sign was a drop in fuel economy and diesel smell after I parked.
Are they selling DF1 or DF2? How cold was the resent cold snap?
I still recommend a shot of Diesel Kleen and the Italian tuneup and reassess.
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  #19  
Old 02-07-2008, 11:58 PM
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Hmm - well I always smell a diesel exhaust odor after the commute (it's not a new thing at all). It dissipates quickly.

Diesel fuel smell? Not so much - and after sniffing the inside of the fuel tank cap just to assure myself that the smell I usually smell after driving is not the same as that of fuel, I am pretty confident. The smell I smell when I get out of the car is the same smell I detect if I take a whiff of the tailpipe after shutting the car down. So odor-wise, I would say nothing has changed at all since I bought the car four months ago. Not to say I might not have an exhaust leak somewhere, but perhaps that is for another thread.

The cold snap has really been over the last two weeks or so and has been at most 10 degrees (C) below normal. The gar is garaged underground - so the temperature it spends most of its asleep time is roughly room temperature and is very constant.

As for whether I am getting #1 or #2 fuel - not sure. I'll give my station a call sometime soon and find out for certain.

As for next steps? I am going to take the italian tuneup recommendations to heart. I have a few good hills and long sections of quiet road I can use for this, so it['s just a matter of finding a good time (and safe weather) to do it. I may also try some DP and see how that affects things. I'll report back how this next tank does me.
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Last edited by xdjio; 02-08-2008 at 12:05 AM.
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  #20  
Old 02-24-2008, 02:26 AM
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Update!

So, to give you guys an update! I ran a new tank through the car since my last post on this topic, and I was sure to take the car out and run it fairly hard a few times.

Results? Back to exactly where I was expecting: 21.5 mpg (90% city driving). That's up from 18 or so.

Looks like I have a good excuse now to take the car out and drive it hard every few weeks.
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  #21  
Old 02-24-2008, 08:52 AM
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What about....

..... the potential for your odometer to be slipping?

W123 speedo heads are notorious for having a gear slip on the shaft, see archives.

This would cause the odometer to register less than the total miles traveled, resulting in a percieved loss of fuel eonomy.

Jim
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  #22  
Old 02-24-2008, 09:13 AM
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Quote:
Originally Posted by xdjio View Post
Results? Back to exactly where I was expecting: 21.5 mpg (90% city driving). That's up from 18 or so.

Looks like I have a good excuse now to take the car out and drive it hard every few weeks.
The SD gets a consistent 27.5 mpg on winter fuel. The number took quite a bit of effort to achieve and includes 85% highway driving at 65 mph. However, I do use 6 oz. of Power Service conditioner on each 17 gallon fill. I cannot provide data that supports any mileage increase on an individual tank due to the Power Service, however, I don't do any Italian tune ups and the engine doesn't ever smoke or accumulate carbon deposits in the cylinders. It sees 4000 rpm once ever month.............if that.

I'm not a fan of beating on an old engine in an attempt to "clean it out". There are products that will accomplish this over time with good results.
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  #23  
Old 02-24-2008, 11:19 AM
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Well - in this case "hard" meant one journey up to 4000, with some highways cruising around 3000.

I do have some diesel purge I need to run through it, but I may try some other products as well - if recommendations are forthcoming.

As far as my odometer accuracy, well - I last checked the odo a couple of tanks ago and was able to confirm its accuracy to a reasonable degree (at least to 1/10 of a km). I may make a regular habit of checking its accuracy.
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  #24  
Old 02-24-2008, 12:27 PM
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Thinking outside the car.

Quote:
Originally Posted by xdjio View Post
Hi guys,

So, typically with my driving pattern (about 90% city, extremely short trips, cool weather) I get about 21 or 22 mpg. When I've driven a tank of mostly freeway miles, I can see up to 24 or 25 mpg. This consumption been fairly constant over 5 or 6 tanks. I always fill up at the same pump at the same station, so I am pretty confident about eliminating that as a variable.

These last two tanks, I've noticed my fuel economy get noticeably worse - like 19 mpg. This started about two or three weeks ago. The only thing I have personally changed since then has been my primary (inline) fuel filter. I've checked the hose clamps repeatedly for leaks and it seems to be just fine... unless maybe it's a really slow leak I am just not noticing.

I haven't checked tire pressures (but will) but I can't think of anything else, unless I am suddenly getting winterized fuel - but this late in the season?

Any other things I ought to explore?
Well since most of the car ideas have been covered, how about taking the bus or a bike for the city trips?
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  #25  
Old 02-24-2008, 12:37 PM
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Bike is always a good plan - however now that things are back to normal, I think I will keep on top of my odo and fuel consumption, and see how things continue to go.

Diesel Purge probably wouldn't hurt either!

However finally, it's starting to get just warm enough here that I might consider commuting by bike.
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  #26  
Old 02-24-2008, 12:40 PM
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Quote:
Originally Posted by xdjio View Post
Bike is always a good plan - however now that things are back to normal, I think I will keep on top of my odo and fuel consumption, and see how things continue to go.

Diesel Purge probably wouldn't hurt either!

However finally, it's starting to get just warm enough here that I might consider commuting by bike.
Or just take an occasional trip to Bellingham. Of course the long wait at the border will probably foul everything back up. You guys got all the "rain" we did this week. The sunny 10 degree kind. Just right for biking.

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