So I recently purchased a 2006 LR3 HSE-7.
Shortly after my first gas fillup with 92 octane/ 10% ethanol my CEL came on. I had the codes read and they were P0171 and P0174 which I have researched and found to potentially mean several things(vacuum leak, MAF...etc).

My last fillup was at a different gas station with 93octane / 0 ethanol. The CEL went off shortly after that.

I was in a bind yesterday and purchased 93/10 again and the CEL came back on.

Has anyone found any correlation to gas used and the CEL with the codes 171 and 174?

 

Shouldn't be, those codes are not fuel generated.

 

it could be clogged fuel injectors or an air leak.

Generally we smoke test it for leaks. If no leaks are seen then we perform a bg fuel injection service to clean up the injectors.

 

Update:

I filled my tank again last night with 93/0 and the Check Engine Light went off for the first time since my last 0 ethanol fill-up.

I understand that the codes are not fuel generated, but the codes do read that Banks 1 & 2 are running lean.

In my understanding of combustion, lean means that the ratio of fuel/air is low. This could be caused by too much air in the mixture or too little fuel in the mixture before combustion. Too much air could be caused by an air leak and too little fuel could be caused by bad/clogged injectors. Or a number of other things could be wrong, such as a faulty MAF which could give a skewed fuel/air ratio reading.

Without getting into too bogged down in the details.... I believe the ethanol in the fuel could be lowering the fuel/air ratio as ethanol has a lower energy density and burns less air in the combustion reaction.

I am going to run a couple tanks of 0 ethanol fuel before trying a half tank or so of 10% ethanol fuel to test this.

I may be completely "off of my rocker" thinking all of this, but it all just seems too coincidental. Especially since the engine was designed to run on a minimum of 91 octane with 10% ethanol.