still learning about my newly purchased '05 roadster...owners manual says 8 qts of synthetic !? surely a standard high quality 5W30 won't hurt? also, for simple driving around without demanding max performance, 87octane won't harm the engine, will it? Any thoughts, advise, comments?

 

Mobil 1, 0w40 is highly recommended. $25.00 for 5 qts. at wally world. DO NOT USE DINO OIL! Gas,....I've used 89 octane on occasion, it was a bit sluggish. Spring for the 91.

 

I seriously doubt that you'll find anyone here that will suggest that anything other than manufacturer's recommendations will be OK. Don't mess with these things unless you want problems down the road. The engine has very close tolerances and the wrong oil can cause blockages and overheating. 0W40 Synthetic costs more but has a longer interval between changes. Low octane fuel can result in o2 sensor failures and expensive repairs. The cars get great mileage and the savings on fuel costs aren't worth the cost of repairs.

 

Do what you want it is your car. When it comes to sell it people can see how you treated it and make their buy or ignore choices based on what they read.
Why go against what is recommended, if you cannot afford to keep the car in an approved manner within reason you should not have purchased it.

 

Mobil 1 synthetic or nothing else. 91 octane or greater gas. It's only an extra 2-3 dollars a tank.

 

Synthetic is fine, after all the Germans invented it for Arctic conditions, makes sure even cold oil can flow properly through small passages Not so sure about the usefulness in Florida though.


As to 91 octane, that is sooo last century for a n/a engine and can put down to the three valve design which needs two spark plugs both in the rong place. Modern engines of the same displacement and compression run on 87 because they have four valves and one plug in the sweet spot (and VVT i&e which helps. My tow car has a DOHC 3.6 like that with 290 hp, 10.25 c.r. and is happy on 87 (or moonshine)).


The major improvements I have seen in the last decade are in increased power and combustion control. The next step requires direct injection and near diesel compression ratios.


For now I fill at 1/2 tank and alternate 93 (Sam's) and 89 (Hess) to average 91. No sluggishness noted. On a long trip with a light load (guaranteed with the absurdly low gearing - 6th is the same OAR as 4th was in my Fiero GT)) I suspect 87 is fine.


ps low octane/high temp/high load results in detonation which can burn valves, put holes in pistons and make everything in the combustion chamber look nasty. I suspect O2 sensor failure would be a secondary effect when the oil burning starts.

 

As stated, it's your car but 0W-40 is used on many European cars. There are other good synthetics out there, I use Royal Purple with no issues. As for the gas, it would not make sense to risk sensor malfunction and engine damage to save a few semoleans. Treat the car as if you love it.

 

At the same time, you are liable to lose power if you run too high an octane since the higher the octane the slower it burns and the more advance you need. 91 is not common where I live so I mix 93 and 89.


To properly burn higher octane you would need help from a tuner. I am surprised that the N/A and Boosted engines have the same octane requirement.


Yesterday was 7 gallons of 93. Suppose I could split fill but do not feel that is necessary.


I suspect that is 91 octane at sea level as I am, at high altitudes such as Denver, it is less.


When lead went away there were issues with exhaust valve seat recession but just about everything has hardened seats these days. Still I like the fact that the 3.2 seems to be a cool running engine, mostly reporting 185-190.


Also yes you can really damage an engine with excessive detonation but the sensors would be the least of your problems (and anyone who cannot feel detonation has a different problems) but the first thing that will happen is the MPG will head for the garderobe and if you watch you will see almost constant knock retard going on.


Old pushrod engines (the Hemi has many of the same issues and some of the same kludges like dual plugs) have the same problem but moreso as a 4" bore makes the detonation issue worse than for the XF. The 400RA in my Judge is also 10.25:1 (and is optimistic) but wants/ needs 98 Research which is about 94 PON so I run 93 plus additives (most octane improvers can add almost one octane number).


If anyone wants to discuss the magic of combustion let me know.

 

^^ To save everyone time looking it up :

garderobe : medieval word for toilet.

Our friend padgett is a medieval kind of guy ........

 

With antique armour always tilting at windmills...

 

Use only oils on the lists 229.3 and 229.5 All are synthetics. I use Mobile 1 5W50 due to the heat in GA and most here think I am nuts. But it is on the list. 0W40 Mobile 1 is cheap at Walmart, why not use it?

The manual says 8.5 quarts, but I stick with 8 so my "HI" alarm light will stay off.

91 Octane or higher only.

Trying to save money like you are is understandable - but wreck less. THere is a REASON the factory tells us what they do - many reasons, in fact. Search the tech sections for the oil lists, but I'm here to tell you, 0W40 at walmart will be your best buy. I also recommend FLEECE type filters, not paper. If you start this engine cold at 50 degrees and rev to 2000 rpm, your oil pressure exceeds 100 PSI. Don't put paper in there.

 

You mean there is no pressure relief valve ? Used to be a concern with very high oil pressure that the bearings would erode, that may be passé.


Back in the day the rule for race engines was 10 psi/1000 rpm hot.


Once upon a time there was a mfr that specified synthetic oil in order to meet a EPA MPG goal. A second reason was for extended change intervals. Neither had a technical reason.


My point is that without knowing the design requirements that called for synthetic, we are just guessing as to the need.


OTOH I understand the reason for a 91 octane requirement. IMNSHO it results from poor design decisions (anyone notice that the current Hemi has the same issues - one exhaust valve and dual plugs) but can understand it.


The oil requirement OTGH & 8 quarts instead of 5 is less clear unless there is an expected condition in which oil starvation may occur. Both could address that.


The Mercedes specs indicate that the reason is for extended oil change intervals, use of the FSS, and a 1% fuel savings, and not that there is anything wrong with dino oils:


"MB sheet 229.3 approved oils
for passenger cars with gas and diesel engines with extended drain interval indicator FSS up to 20,000 km, or 40,000 km - 25,000 mi, current minimum spec for 1998+ MB engines, min. 1.0% fuel saving compared to 229.1, based on ACEA A3 B4.


MB sheet 229.5 approved oils; "MB Longlife Service Oils"
for passenger cars with gas and diesel engines with extended drain intervals beyond 229.3 oils, to 30,000 km, min 1.8% fuel saving, first oils introduced summer 2002. ACEA A3 B4. For gas engines of the M100 series, gas engines of the M200 series and diesel engines of the OM600 series (not models with Euro 4 diesel particle filters).
229.5 engine oils must be used with fleece oil filter designed for use with 229.5 engine oils."


See engine oil difference between 229.3 and 229.5 - Mercedes-Benz Forum for more than you ever wanted to know.

 

I'm sorry but it appeared that your logic is just because the manufacturer told us to we shouldn't have to unless they prove there is a reason? I would rather do it until someone I trust, ie not an individual or competing product manufacturer, proves otherwise.

I have sat through a couple SRT engineers seminars with the Viper club while they explained to us why they required 0-40 synthetic motor oil. I believed their logic.

 

Did I say that? Hell, I'm just telling you what the oil gauges on BOTH of my Roadsters have displayed. Two cars, two gauges - within 10%, same readings.

 

No, just said that the reason for synthetic might not have anything to do with engine life.


I know of three reasons to use synthetic instead of dino (and some "synthetics" have a lot of dino in there):
1) longer change interval
2) increased MPG
3) better flow qualities (viscosity) when cold.


In central Florida, (3) does not really matter, (2) is of interest only to the EPA and for advertising, and I change oil and filter in my other cars at or before 3,000 miles. (1) and (2) were specifically mentioned by MB. Was there something else ?

 

Padgett I am more than a little curious as to why you think you know better than the MB engineers as to the use of two plugs and the placement thereof. You are aware that these plugs do not fire at the same time thus providing an extended spark event. And by the way the MB 3 valve engine was chosen to provide power to the Pagani Huayra, one of the elite supercars on the planet.

 

The main reason I switched ALL my vehicles to synthetic is SLUDGE. I've seen some pretty gunked up engines that were fed dino. But, I've seen a few that were fed Mobil 1, and had no sludge at all. That's reason enough for me.

 

Didn't say I knew any more than any other engineer, just saying that there may have been other criteria involved (and the next generation did go to a single plug four valve design just like the Pentastar).


Do know the reason for a 90 degree V-6 is generally to use the same assembly line as a V-8.


Also the Chrysler Hemi also has a similar dual plug staged spark design that was necessary to pass emissions testing with a pushrod engine.


So maybe Pagani had a special need or MB made an offer they could not refuse or just someone liked the design. Dunno. Don't really care. Just have reason to believe from a design standpoint that it is a kludge from the last century that had to be built with certain restrictions.


From a pre-VVT viewpoint it is a reliable design to fit a nitche. From today, not so.


Just saying that if I had a major engine problem, I'd sell off what was usable and install a DOHC 4-valve Pentastar. No EGR, no secondary air pump, no dual intake runners just six plugs, available parts and a bellhousing/clutch from a Wrangler that bolts up to the transmission. Throttle body is even in about the same place.


Not saying it would be easy but would have 300 hp NA on 87 PON when done and an engine that is likely to stay in production for a while (over a million on the road already).


May never come to that, I tend to take very good care of my cars and have one engine that still makes A Lot of HP and is closing on 45 years old, just have built some "interesting" ones before and I really like DOHC sixes. Have one in my tow car.



ps worst sludge I saw in an engine was a SBC that had been on synthetic from day one. OTOH have pulled engines I bought new that were dead clean inside at 80,000 miles despite nothing but dino oil

 

Why do I feel slightly less intelligent now?

 

NP. Ignorance is curable but stupidity is forever.


Credentials are available on request but lets just say I have a few.