2008 ML320 CDI questions (cold starting)

[awd_rules3830]

My parents decided it was time to replace the 2003 gas guzzling Ford Expedition with something more fuel efficient and something that would legitimately last 10 years plus without trouble.

It came down to the Lexus RX 400h or a Mercedes Diesel. Its a car for my mother; dad wanted the RX 400h, I wanted to get the diesel. I took mom to test drive both; she liked the Lexus because it has some feminine appeal but she also liked the body style of the ML class.

I had done my research and was worried about battery replacement issues after the warranty period on the Lexus. I started a thread actually on LegacyGT.com (i'm a Subaru Legacy owner myself) called Diesel Vs. Hybrid and it turned into 15 debate and it is still going. I was also impressed with the mileage that was reported on Edmund's.com that seem to be around 27 mpg (what is it reported at on the sticker) highway in the ML class.

We test drove an R320 CDI and an ML350. Mom liked both but thought the R class looked too minivan-ish. I tired to get her into a E-class for the 36 mpg highway mileage but mom didn't want it.

The dealer obviously didn't have a ML diesel and no other dealer around wanted to give theirs up on the hope the could sell them with high prices for gas and lower diesel prices (i guess). Thus we order one ... It will get here at the end of September lol.


I have questions as to how well the engine cold starts. It can get quite cold in nebraska but I have heard good things from an R-class diesel review that was taking into the mountains for a ski trip or something and the reviewer said the car performed nice and got 26 mpg overall or something. He didn't mention any cold starting issues at least.

I'm kind of vaguely aware of common-rail diesel technology and i'm not even sure if this new engine even use glow plugs. There was no wait time for the diesel in lot when drove it for what would usually be plug warm up time. You just turned the key and the car started. There was a light diesel rumble but nothing horrible or anything. Once cruising on car was VERY quiet.

Advice, explainations lol.

[Kajtek1]

cdi doesn't require plugs warming before start. Actually I had commercial diesel from 60's that didn't have glow plugs neither, but cold start wasn't its best part. Actually it didn't have good parts
Anyway. I would love to drive cdi, but they were never sold new in CA and not likely will soon, if ever. Knowing that diesel is good for over 1/2 mil miles and MB cars very often show showroom condition after 10 years, you guys might get bored with the car, before it ages. Not that this is a bad thing.
The worst thing that can happen on this engine is necesity for plugging in block heater. But I don't think you'll have to do it above -20F.
How much more diesel cost vs gasser?
Congratulations on the choice and welcome to the forum.

[awd_rules3830]

it was 30 cents less over labor day to regular.

[Kajtek1]

I was asking about diesel option in ML.
We own E-classe one with diesel and one with gas engines. The operating cost of diesel is like 60% of buying the premium. The gasser is 4-Matic but still.
On the top of that on gasser reaching 100k the wear out is becoming an issue, while on diesel with 240k nobody's worry.

[Diesel Benz]

A CDI would have glow plugs. Modern glow plugs are very quick though and if the engine is half from normal temperature, no pre-glow is needed. At normal external temperatures when the engine is cold, one can see the glow indicator turning on and disappearing almost immediately. A difference to gas engines exists but not really significant like on cars 20 years ago.

The CDI would likely start OK at -20F but you have to use good engine oil, 0W/something or 5W/something preferably as you would on any engine at that temperature. One shoudl still avoid cold starts at -20F where possible, with any engine in my opinion.
I would use STH (not sure if you can have that in the US) or a block heater if the temperature was below 15F! The new engines have aluminium block and a true block heater is likely not available, one should be careful to pick up one that really works.

The most important thing at -20F is that the diesel fuel is made for low temperature, otherwise paraffine clogs filters or even pipes (the filter is normally equipped with heating, and once you get the car running, the CDI anyway warms up the diesel oil more than the older engines did).

[awd_rules3830]

so at what temp would the glow plugs add heat?

like ... 40 degrees F ???

[flyboyike]

Originally Posted by awd_rules3830

so at what temp would the glow plugs add heat?

like ... 40 degrees F ???

Probably lower than that. Anyway, the truck will start fine, no worries.

[Kirill]

If question is hybrid Lexus vs diesel Mercedes and outlook is 10 years. I think diesel Mercedes wins with no contest.

I just don't have confidence in long term hybrid system reliability.