Blackstone's analysis might be good, but their tech's readings of those numbers leave a lot to be desired in many cases. You can entertain yourself over on bitog.... believe what you please, it makes little difference to me, my point was just that a 5w30 shearing to a 5w20 isn't earth shattering news.

 

Maybe this needs reiteration - TSB EG006-06 says as of March 29, 2006, ALL new Lexus vehicles are getting ILSAC GF-4 5w-20 as their standard fill, from the factory since February, 2006. So anyone taking delivery by the end of March or later very likely had 5w-20 oil in the crankcase.

5w-30 shearing to 5w-20 in less than 5k miles is news, and should never happen in a car engine that quickly. In a bike, sure, it goes through the transmission and suffers a lot of mechanical damage from the clutch and gears, but in a car engine with a gerotor oil pump?

 

If you are asking ME if I cleaned my K&N, then no. I don't even have a K&N, and my HKS filter has been in the car for just a few weeks. I guess that could be the cause, but I would be surprised.

I've been buying gas from the same 2 stations I've always got it from. All of them switched to E10 earlier this year.

 

i don tknow, call me retarded ...what is ILSAC GF-4 and do you recomend using the dealer to do the oil, or would it be ok to go where it take all my cars? and when would it be ok to switch to full synthetic, i ask becuase i know that the service intervalls are longer then the standard 3k miles..i just dont want to foul something up.

 

If you are a "regular joe driver", then you will be TOTALLY fine going with the recommended 5K interval. I sent my break-in oil in for analysis by Blackstone Labs after 5K of pretty hard driving, and they said everything was fine.

 

Hey Gernby, did you figure out if it was the HKS drop in filter causing the -1 mpg?

 

Nope. I'm just going to change back to 5W-20 in 5K miles, and see if it improves.

 

I must swallow my pride, and admit that I was wrong about the oil causing my reduced fuel economy. I still don't know what the deal was, but I've been averaging over 22 MPG for weeks, and haven't changed a thing that I'm aware of.

Anyway, my apologies to those that I argued with above.

 

No apologies necessary, don't sweat it, it's all good. We were all just brainstorming along w/you to figure out your mpg drop. I have a new theory - when you installed your JoeZ & HKS, the ECU may have detected the change and started running richer to compensate for the add'l air flow ?!? After a few weeks of normal running, the ECU self adjusted again and now you're back to status quo mpg - your oil change just happened to coincide with the install of the intake/air filter . . .

 

I seriously doubt the minor intake mods could have been "detected" in any way by the ECU. I think the cause had something to do with my driving habits, as others suspected above. Although I was methodically trying to get good mileage, it just wasn't working as well then as it is now.

EDIT: It could have also been a bad tank (or two) of gas.

 

I wouldn't discount your intake/air filter mod, other forum members have posted that the JoeZ intake adds 5-7 rwhp on their dyno runs, add the HKS filter and it's no longer a 'minor' change. If the ECU can detect octane drop and retards ignition, it should also detect the added air flow. Either way, you're back to normal mpg, so life is good again . . .

 

The ECM doesn't detect octane drop. It detects audible knock in the cylinders. It doesn't care what the source of the problem is (octane, overheating, clogged injector, etc.) it just defaults to retarded ignition timing to prevent the engine from detonating itself to death.

More or less air means nothing to the ECM. It's using a wideband O2 in front of the precat to determine a/f ratio and set it to what the ECM is expecting (maybe stoich, maybe not). The only time the intake could possibly affect a/f in a bad way is at WOT, and even then, when you consider how small a hole you need to make 306 hp, the intake is massively oversized. Yes, the first couple of minutes you change something it will upset the correction factors, but short term trim will kick in very quickly and sort that out, even at WOT.

 

im closing in on 10k miles and i want to change to synthetic, brand doesnt matter right?

 

Well, it's truly personal preference and everyone has a different opinion. I still prefer dino oil, but I'd bet that most folks choose Mobil1 - it's reasonably priced and available just about anywhere. IMHO, you should try to stick to one brand rather than buy whatever synth happens to be on sale before your next change . . .

 

Brand isn't a big deal. Availability is probably one of the more important features. Exotic synthetics may be pretty hard to find if you need to top off and you're far from home.