Update: after completing the EGR valve cleaning and taking the vehicle on a 600 mile RT, I note my fuel mileage has increased from around 35 to 36.8. Previous 35 MPG reading was recorded during a 6400 mile cross country trip several months ago.

Traveled routes (both pre- and post EGR cleaning) were a mix of highway and city....mostly highway.

Of course there are a lot of other variables but it does make sense that a sticking EGR valve might reduce fuel mileage.

So here is another benefit to checking your EGR valve and cleaning it. Get out there and check it

__________________
-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

Member GregMN has done a lot of CDI research into the disablement of the EGR valve on the CDI - IIRC. He has certainly written about it in the not too distant past - like in the last month! I'm surprised he hasn't chimed in on this thread!

__________________
'06 E320 CDI
'17 Corvette Stingray Vert

Yes, a little joke there to see who was paying attention.

I cleaned the EGR when I got my CDI just because I'd read about it getting dirty and did a lot of "new to me car preventative maintenance." The car performed noticeably better.

My understanding however is the EGR cooler also gets clogged up, and just cleaning the valve obviously isn't cleaning the cooler out. I like to think my daily full boost trips to the redline in a gear or two is working to keep the EGR cooler blown out. I've read of people pulling the cooler and manually cleaning it but it is much more labor intensive.

__________________
68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

My 06 CDI is still in transit, when it gets here I plan on doing the

EGR Delete here

__________________
1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250, Dec 2024 145,000 miles

__________________
'06 E320 CDI
'17 Corvette Stingray Vert

After 28k miles since my first cleaning, my EGR valve began causing my '05 E320 CDI to go into limp mode again. No codes on dash. After removing the EGR valve, I noted it was again full of dry carbon powder.

This time I just used a small toothbrush and some compressed air and was able to clean it completely this way. Instead of graphite, I applied a few drops of Mobil 1 5w 30 to a q-tip and lubricated the armature under the plastic cover of the valve until it sprung closed. It now is operating correctly again.

It will be interesting to see if the carbon mixes with the oil and stops the arm again.

I think that the EGR does not have to actually be removed. You can simply remove the plastic cover and vacuum the powder out and then lubricate the armature and replace cover.

I will admit I have not looked at the EGR valve since I cleaned it the first time at about 103k miles. But given not having to remove the entire unit, I will begin inspecting at every oil change.

__________________
-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991