I noticed mine's kind of worn, am replacing it, but am wondering if this affects fuel/air mix. Is air past the dipstick "unmetered air" for the lamda to compensate out?

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Gone to the dark side

- Jeff

The crankcase in the 104 vents into the intake crossover tube, which shouldn't really see a vacuum unless the air filter is packed full of crap. I'd expect to have oil vapors leaking out past a bad oring than to have air leaking in past it. Regardless it's cheap enough to replace it so just do it already

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

Dipstick O-ring has no relationship to fuel/air mixture. It's a good idea to replace it if it's worn/dried out.

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Fred Hoelzle

I changed mine.

On many recent Bosch fuel injected engines, pulling the dipstick while the car's running will kill the engine.

It's important.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

That's why I was wondering, lots of engines will throw a code if the dipstick isn't seated as it introduces unmetered air. No big deal, just wondering if my car was compensating and will need to adapt now that there's a fresh O-ring.

I have never found a day that I regret buying a high-quality O-ring assortment. That once every couple of months that you find a marginal one, pull out the assortment and install a new one, ... worth the savings in time/fuel/mileage alone.

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Gone to the dark side

- Jeff