cdelena

[QUOTE]Originally posted by Pinky
[B]I have been told that switching between dyno oil and synthetic isn't a good thing due to seals within the car going bad.

jschmidt

Since "oil makes horsepower" is a myth (OK it may SAVE a tiny amount) and oil has only a very minor effect on mileage, I'm guessing that there is some other explanation.

As a data point, I get about 24 mpg in mixed driving with Mobil 1. Don't know my HP but I can pretty much keep up with other S2Ks. The idea that the engine uses a loss system for oil is contraindicated by: how much is used, variations in usage (ie. mine uses none between changes, others use some) and emissions requirements.

If your mixture is really rich you can "wash" the cylinder walls leading to increased oil usage and ultimately wear, but this is old carburator knowledge that probably doesn't apply here.


BTW, I'm guessing the soot you are seeing comes from incomplete combustion in the cold engine, not transfer of carbon.

I can't figure how oil is the cause of your experience but, as always, (your) experience is probably more valuable than (my) theory.

cmnsnse

Hey UL,

You wouldnt happen to know the piston to cylinder clearance would you? Ive been stalling on getting the manual
The oil ring does seem to be very thin though.

Im sure viscosity plays a major roll in cylinder compression vs blow by. So pending investigation, we may be trading lower pumping losses for lower cylinder HP? That by changing from conv. 10w-30 to synthetic 5w-30?

I figured my mileage was worse because I have 33,000 miles, but its worth throwing conventional in there for a few miles.

Big Al

I related the presence of soot to oil consumption in my car. It had a bunch of soot for the first 3000 miles and it also consumed oil. At a little above 3000 miles it stopped using oil and the soot went away!

WRS2K

I just bought a case of 10w-30 Mobil One. I'm at 14K right now. Don't know whether I should just continue the dino stuff or go synthetic after reading some of your thoughts.

The Reverend

Hey UL, do you usually fill up with gas at the same place or do you go to different places all the time? I ask because that could account for your difference in milage. Some pumps fill you up to the brim before the click off while others smell gas and click off. My point being, if you filled up at a generous pump right before your oil change, then you change your oil, fill up at a pump that is a bit too sensitive and doesn't fill it all the way - and then you get a reading that you just filled up your tank, but it only took 9 gallons to do so. When in actuality, you really used 10.5 gallons on that tank and your new tank of gas isn't quite full. Get what I mean? I just can't believe changing from one good oil to another would make anywhere near a 4 mpg difference with all else being equal.

Sparky

[QUOTE]Originally posted by Luis
[B]At that moment, my oil temp gauge has barely moved from it's resting place.

Luis

[QUOTE]Originally posted by Sparky
[B]

So, exactly why would oil temperature be a better indicator of when it is safe to VTEC than water temperature?

marcucci

OK, Luis, if this is the case, can you relate this phenomenon to oil pressure? If the oil requires 6 times much more pressure, how come most vehicles, before even being "warm," have normal pressure readings at colder temps? I haven't seen a car yet that right after startup on 10-30 didn't run about 30psi at low RPM and 55psi at high RPMs. I would suspect pressure to go with with resistance.

While the oil may flow as easily, I would suspect it to flow easily enough to lubricate the engine sufficiently. If not, I would suspect Honda of leaving the rev limiter in longer, until the engine was at operating temperature for a "safe" amount of time.

You never did answer, what's the lowest discernable deflection on your gauge?

ultimate lurker

There are so many considerations here, which is why I was hesitatnt to post until I got more info.

But first, I fully agree with you Luis that you want the oil temp up to spec before hammering the engine. There is a reason why top race teams preheat oil and coolant before even starting the engines. When we do precise dyno testing we always use oil temp as an indicator of when to test (along with water temp).

In the case of synthetic vs. dino oil, I've always been a big fan of synthetic. I've used Mobil1 in all of my cars and never noticed any of the fuel consumption issues that I've noticed on my S2000.

With respect to the questions, I usually tank up at the same places. As I said, the average mileage gain seems to be about 10%. I have only used the original factory spec oil - i.e. 10w-30 (or was it 10w-40, I know my CRX uses 5w-30, don't worry, I always check before I buy - either way, I've never changed weight :-). In terms of ring tension/clearance, my manual is in the garage, but I do know the F20C runs a very low tension oil ring. You kind of have to if you want to rev to the moon.

Interestingly, I just changed my CRX from synth to regular oil to see what happens. So far, no difference in mileage (might be a bit lower even) and if anything performance seems a touch off - but again, that's a butt dyno reading, so I really don't count that. However, the CRX runs higher tension rings and was tuned (I mean pulsewidths, timing, etc.) on synthetic.

Remember, all engines burn a little oil. Does the type of oil have an effect on the combustion process? Or does it have something to do with the ring/cylinder interface? Does the higher shear strength and greater stability of Mobil1 have a detrimental effect? Harder to scrape off the walls, especially with low tension rings? I don't know. Stay tuned as in another 1000 miles or so I'm going to go back to synthetic and see what happens. I'm also going to talk to some more rotary folks and get their take.

UL