For an E420 (124) engine? I am not using synthetic and don't plan on it either. Just wanted to know which is a preferred brand for a rather warm area like Houston, Texas. Some of the brands been used with this car include Castrol 20W-50 and Mobil 1 20W-50. I need to stick to one solid brand and weight all year round… is that possible?

I don't believe there is a 20W-50 Mobil 1. Perhaps you are thinking of Mobil's petroleum based oils.

Everybody here has their own favorites and rationale for choosing it.

My personal choice would be 15W-50 Mobil 1 changed every 3,500 miles or six months (whichever comes first).

Frequent changes of name brand oils that meet the viscosity recommendations in your owner's manual should be fine.

Naturally, you should use OEM filters.

You mean Mobil 1 20W-50 is petroleum-based vs Synthetic? if that is the case, then yes I am using the petroleum based. Actually the MB dealer did the last oil change.

The dealer recommends changing oil in 6 months or 7000 miles and I want to change it at 3500 intervals. Do you recommend changing oil filter after 3500 miles or wait until the 7000 miles?

Changing oil without also changing the filter is like taking a bath and putting the same dirty socks and underwear back on that you were wearing before the bath. If anything, you'd be better off changing the filter and not the oil. It collects the trash.

If you change oil, also change filter.

Forget all of the "extended" non-sense being sold these days. It's nothing more than marketing hype used to sell cars. If your plans for the car are short-range, then you can follow the new philosophy; otherwise, do as Larry Bible has often advised.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Mobil/Exxon's synthetic based oils are called Mobil 1 (ONE). All other Mobil oils are petroleum based.

You could tell I don't know much about oils. I was planning on using the Liquidvac and replace the oil "in between" oil changes.. but I guess you're recommending changing the filter as well.... That should not be a problem since the OEM filters are low cost maintenance items anyway. Do you agree with the vac method and still have it drained from the oil plug once in a while -probably every other oil change or so?

I've been threatening to buy a Topsider oil evacuator for a long time but still do it the old fashioned way. The only problem with draining is that you have to remove and replace the cover under the engine and then you have to transfer the oil from the drain pan into some other container.

On the other hand, when you drain it you get an opportunity to see if you have any leaks. When I get too old to get that cover off I'll do it another way (or buy a new BMW or MB and let the dealer do it).

Just spoke to the shop foreman at the MB dealer and he said that there are no problems using vac system or topsider to evacuate oil as long as new filter is installed every time. so i will use the vac the next time it's due for oil change and see how that goes. I prefer not to go through the hassle of removing the bottom cover and drain the oil... I asked him about the oil change intervals and he said that changing it at 3-3.5k is a little overkill and he recommends 5k instead. his argument is that the 3000 mile rule was made over 30 years ago back when there was only one oil weight before the new oils and viscosity we have now. So in any case, adding fresh oil after 3K or 3.5K will not harm anything and i will still do it at these intervals since fresh oil means cleaner engines and with the vac system it shouldn't be that bad of a chore. By the way, he also said that MB is now using 40W-15 Mobil oil for older cars in place of 20W-50 .