More knock on higher octane?

[Lex]

Here's a strange one boys and girls. I live in Canada close to the US border and sometimes I'd cross over to get gas. When I do, I usually get Texaco 92 octane since it's close to the border.

When I get gas in Canada I use Chevron and I get 94 octane.

The strange thing is that I get NOTICEABLY more knock on the 94 octane keeping all other parameters the same. I have noticed this over several fillups and I also get less performance on the 94 octane.

Here are two logs. The ambient temperatures are very very similar and the driving conditions are the same - on the highway with prior normal driving. 4th gear.

92 octane texaco is the first graph and 94 octane chevron is the second

Anyone have a clue why this is? Like I said, this is very repeatable.

EDIT: Added a third log with Husky 94 octane. Same conditions, same temp, same 4th gear. Notice the very very low knock. It contains 10% ethanol.

[Haltech]

Could be a bad tank of 94. It happens sometimes.

[Lex]

Originally Posted by Haltech Could be a bad tank of 94. It happens sometimes.

I've had the same result for many tanks of the same chevron 94. Chevron 94 that I got from that same gas station knocks like a bitch and that texaco is much much better.

Anyone had similar experiences?

[Boother]

I have the EXACT OPPOSITE experience. I get large knock readings all over the place on 91 octane and when I put 94 in, the knock almost completely stops.

[mordant80]

Personally, I'd quit buying from that Chevron station. Sounds like that gas isn't quite up to par.

[smakdown61]

Theres a shell station near me that I noticed kept giving alot more knock whenever I filled up there. Just a crap gas station.

[AlExTEK]

The best pump gas for our MS3 is Shell 93 octane. More mpg. With Texaco 93 I get 300-310miles on a tank and with Shell 93 I get 340-378 miles per tank.

[SgtP]

i only buy shell or sunoco 93 and never see any knock.

[MS6_Auburn_Fan]

I'm sure I will get flamed for this but I usually buy 93 from QuickTrip and rarely see if ever see knock. Because of the gas shortage down here I filled up with 93 from Shell on my way to a jobsite and have been seeing knock much more frequently than I ever have before.

[oskinosmee]

Shell gave me 3.5 knock, bp gave 0.4 FUCK YOU SHELL 10% ethanol

[Lex]

I see lots of mixed opinions. Some people say Shell, some say no to Shell. I'm willing to give other gas stations a try. I don't think shell sells 93 in Canada. Weird thing is that Texaco is related to Chevron (if not the same thing).

Is it more like a particular gas station to station issue or is it the additives that cause this? In my books 94 octane should be 94 octane.