280SL and modern gas
 

Hi...
I have a '69 280SL...my most reliable car out of anything I've owned new or old...always keeps going and going!

Question...anyone have any problem with engine damage with modern gas, especially now that lead has been long gone and there is up to 10% ethanol in many pumps these days? I deliberately keep my valve lash on the loose side to make sure valve seats well and dissipate heat, but as this is the original head, I'm beginning to worry about not adding an additive to the fuel on an engine designed for use with tetra ethyl lead. I'm very suspect on additives...most are nothing but mystery petroleum distillates that do nothing except make the manufacturer and distributor a ton of money, so if anyone has found something that really helps, I'd would be thankful to learn about it. I also run regular in my SL but have the timing such that I don't have any pre-ignition, the only difference in grade being iso-octane content.

All Benz had hardened valve seats and bronze valve guides as OEM so no issues with using "unleaded" gasoline. Adding lead to gasoline was mostly an American thing.

Performance may suffer a tad using the ethanol blends but the main problem you will encounter will be the deterioration of the older rubber fuel lines and associated parts. Not a big deal to replace them.

Hi Mike, thanks for your reply. Good to know they had hardened seats back in the sixties...I didn't know that. And correct on the ethanol...the old story was, anything that works with ethanol will work with gasoline, but and polymer/rubber/composition designed for gasoline won't necessarily work with ethanol. So original lines on our old cars may deteriorate a bit faster with domestic fuel with ethanol. Interesting sidebar...I worked under a Nobel Laureate in chemistry (John Fenn) at Yale in a lab many years back (40 yrs),and I remember him saying how crazy it was to do the ethanol additive thing to gasoline....he said that because there are fewer carbon-hydrogen bonds to break, you get less in emissions...but then less power, hence mileage...a zero-sum game, so what's the point?? When he brought this up in DC, he was told it was a 'political decision' to push for more ethanol in our fuel related to subsidies! So there to your point of lower mileage. Question...has anyone seen older MB heads off and any burnt valves in general?

Are you referring to the John Fenn who gave us PCB's? I knew he was a big player in the jet propulsion industry and did his major research in mass spectrometry (I won't lie, I had to look that last part up). I wasn't aware of his involvement with automotive fuels.

You moved in some heady circles.

Burnt valves are generally caused by timing, over heat or lean burn conditions. I have seen heads with detached seats and guides but every time it was due to an extreme over heating condition.

I have a 230SL 5 speed with a 250SE engine. I've been running whatever fuel I could get for the past 25 years and really never have any problems with ethanol. I've had to replace the hose coming right off of the fuel pump once or twice in all those years but I think that has more to with it being rubber impregnated cotton ( or something like that ) than anything else. We use 10% ethanol blend here. Premium is supposed to be ethanol free.


I would adjust your valves to .003 and .007 and use a high zinc content oil. Blends used for diesels seem to work well. Burned valves and heavily worn cam shafts are often due to a lack of valve adjusting. You will always hear a loose valve rocker but you will never hear a tight one.

Thanks for your post...that makes me feel good about the fuel available for my SL. What are the gaps you recommend? Is the 0.003 for intake and 0.007 for exhaust I would imagine...what are the factory specs? I need to do mine soon...it's been some time. By the way, does your 230SL have the early style hubcaps/wheel rings? I think those make the wheels look much better than the full wheel covers, don't you?

Those are the factory specs for valve lash. I have caps and beauty rings on my car.

Through a system of vintage high performance parts on my car I'm getting around 10 km per liter of fuel. Since I installed the larger 82 liter fuel tank I can easily drive 750 km without a fill up. So, I'm getting around 23 MPG US or about 27 - 28 MPG imperial.

Have you checked out the pagoda group web site?