edster75

This is my second year of HPDE's at the Autobahn Country Club in my 2016 A8 Z06. They have Sunoco 260 GTX (98 Octane) and 260 GT Plus (104 Octane). Both fuels are unleaded. I've tried both of the fuels because the difference in price at the track is only .50 gallon. I also have the GM 100 octane tune. Most of the track days last year were 85-95 degrees and humid. Occasionally I get a check engine light but I've never scanned the car to find out what the code is. It usually goes off after a few drive cycles. The car has been running great with no overheating or limp mode. I do run in M mode and try not to rev past 6k.

I recently had a oil analysis from blackstone and it had some lead (48ppm) in it. In the comments section they mention the use of leaded race fuel as a possible source for the lead. Both fuels are unleaded so I'm not sure where the lead would be from. Blackstone did mention that even unleaded race fuels sometimes have a little lead in them. So I checked Sunoco's website and found out that the 260 GX Plus is actually oxygenated fuel. They also mentioned that lead could be from bearings, but our cars don't have lead in the bearings they are polymer coated, and all the other metals looked very good with M1 15-50. I'm attaching the oil report incase anyone is interested.

I don't think I should be running oxygenated fuel in my Z06 with basically a stock tune. What do you guys think? I was also thinking that might be the cause of the check engine light. Although I don't remember if the light came on with the oxygenated fuel or not.

I also have a white tint on the inside of my exhaust pipes instead of the usual black. Would that be an indicator of a small ammount of lead present in the fuel?

Thanks in advance!

kenownr

Road machine

I doubt the lead would have come from fuel.....you only get traces of fuel in your oil and there would only be a trace of lead if any in the fuel. I think the cam bearings are aluminum, so I don't think it comes from there. Is it possible you got some cross contamination from where you put the sample in??

edster75

I don't think I had any cross contamination. I let some oil drain out and put the sample container in the stream and filled it about half way. They have a pretty nice sample kit, btw.

I forgot that toward the end of last year when I had the alignment done that the shop checked the code. It was a P0121 Throttle Position Sensor Fault.

The car is stock besides a BMS Filter, Mamo PTB, Akrapovic exhaust with catless xpipe, and the GM 100 octane tune.

laserdude2215

I don't understand your concern regarding oxygenated fuel with the 100 octane tune. The 260 GTX has no ethanol; 260 GT Plus is only 13 percent. That's just a touch more than what you would find at the corner gas station at 92 octane.

edster75

https://www.sunocoracefuels.com/fuel/260-gt-plus

https://www.sunocoracefuels.com/fuel/260-gtx

Oxygenated fuel needs more fuel flow. I'm not sure if the stock tune would compensate for that.

ForcefedSupra

that looks more orange tint on your pipes. And that could be due to that the 260 GT does contain MMT metallic additve for octane booster, and is bad stuff for your engine. The 260GTX has no MMT or metallic additives. The MMT is what causes the orange brown color.

Svtracer14

Exhaust tip looks like the coating octane boosters such as Boostane leave behind ok O2 sensors and spark plugs.
are your plugs the same color? Seems like something in the fuel that could be causing the contamination in your oil. It only takes a little for detection in oil sampling.

edster75

Quick update. Stopped running race gas at the track and the lead in the oil report went down dramatically. Almost nothing now. Car runs fine on 93.

kenownr

I guess my question would be; any noticeable performance difference seat of the pants or lap times on the 93 vs the race fuel? I'm guessing the cost savings is significant.

tom

Thomasmoto

This is proof of what I've been telling a lot of my friends for years that you can use too much octane in an engine. It's not really hard to do, even easier with engines that are NA.

TJay74

As ForceFedSupra said, the orange tint is from the MMT additive that is added to high octane fuels as a octane booster. GM actually lists it in the owners manual to not run any fuels or octane boosters that have MMT in them. As said MMT will leave residue on the spark plugs, O2 sensors and the exhaust. It can eventually kill the spark plugs and O2 sensors if continued to be used over time. The orange coloring you are seeing is something that a GM tech would have to report about had there been a claim while under warranty.

TJay74

Running too high of a octane didnt cause the lead issue, the type/brand/composition of high octane fuel is what caused the lead issues in the OP's situation.

Thomasmoto

I wasn't saying it did. It was just a general statement about octane.

TJay74

The prob is that on the stocking timing maps GM cars can use every bit of 93 octane and then some, heck 95 octane is about what it takes to keep detonation fully away on modern D.I. GM cars. The timing map is pretty aggressive from the factory since it relies heavily on the timing modifier tables to remove timing due to IAT, ECT and Knock. Eliminating the knock helps insure you are only losing timing to IAT and ECT temps.

RocksZC7

The Engine Masters TV show recently aired an episode about fuel octane versus horsepower. I was very surprised at the results. My takeaway was every engine has a particular fuel octane design point derived from the profile of the combustion chamber, piston top and flame path among other things. The myth that raising octane past this design point will increase horsepower was proved to be false. The LT4 was designed for 93 octane (or maybe 100). Using fuel above this octane rating will not generate any noteworthy HP gains. I highly recommend watching this episode of Engine Masters … great show!

X25

I think that track was either storing different fuel in those tanks, and they're contaminated, or they're putting different stuff there, and fixing the octane with MMT, etc. In short, I'd not trust that track, and would never but anything from them. You should also consider bringing this up to their management.

edster75

None that I could tell. I used HP tuners to log a full 30 min session and didn't see any knock retard with 93. I'm also running the gm 100 octane tune.

TJay74

Short of running a true oxygenated race fuel, you are correct. Octane will never increase the HP. It insures you dont lose HP to knock. I have tons of data logs on GM vehicles since my 2008 C6 Z51, every one of them has shown knock from the factory on 91. Even on engines designed and certified for 87 (2001 Silverado Crew Cab 5.3 4x4 and a 2010 GMC All Terrain 5.3 crew cab 4x4). Not only that I did a bunch of data logs on my buddies 2010 Camaro SS while cleaning up the stock tune, running around on 91 there was knock all over in the part throttle areas and under WOT. Upping the octane to 93 greatly helped and then adding 10%-15% of E85 to the tank damn near eliminated. He just data logged his GF's 2016 Silverado with the 5.3 and saw the same results I have always seen, lots of P/T and WOT knock. The moment he added E85 into the mix with no other changes the knock went away.

The GM timing map is just super aggressive, huge reason why lots of tuners get decent power gains from just working on the timing map and removing timing and keeping the ECM from having to pull timing via the modifier tables.