^^^

Thanks Lisa, your experience is very interesting as you obviously put on a lot of miles and the gas isn't still without sloshing around as it would be for folks who store their car and have the tank full. Also for a variety of reasons I generally keep my tank over 1/2 half full- one is living 17 miles from town don't want to be concerned when I can get to the Shell station with the lowest price or the Sam's Club gas I use from time to time that is usually $0.40 to $0.50/gallon cheaper!

My thought is when above 1/2 full the resistor part of the sender (versus the float end) could be in the fuel. That is when sulfur in the gas (sulfur content is no different Top Tier to not) will attach to the sulfur that is probably on at least part of the sender resistor. (Perhaps one sulfur particle is attracted and attaches to another by epitaxial growth which is an issue in welding where a slag can chemically attach to the same particle on the surface of the solidified weld metal making it difficult to remove. Not a chemist so only comparing with what I know happens with silicon etc in welding!)

I never worried about the fuel sender issue until the C7 as getting to the sender to replace it is difficult. Part of the rear drive train has to be dropped! I can't imagine the local Chevy dealer getting it all back correctly even if on warranty. In my Street Rod, which mostly sits in the garage, I only add Stabil and always have a full tank (being tubbed it is a small one!) However if that fuel sender fails I can drop the tank in short order and replace the whole sending unit - I installed and it's easy! It has a resistor near the tank top and a float and arm attacked to the wiper that contacts the resistor. Considering the difficulty of replacing, wonder why GM still uses this over 75 year old method to measure fuel level! No doubt because it's cheap!

 

FWIW, this is the pic of the C7 fuel sender. Similar to what I have in my street rod. Easy to change with the tank removed! That is the catch!

This is the Service Manual description of what that requires:
Remove muffler
Remove right wheelhouse (page 3-115)
Remove transmission (page 17-283)
Remove evaporator emission hose
Disconnect fuel pump harness
Remove right side cross brace bolts
Remove right side underbody tray
Remove right side fuel tank strap bolts
Disconnect crossover tube (page 9-372)
Remove fuel tank
Remove fuel sender

NOT FUN!

 

^^^^ PATTYFRUITCAKE LOL!
You ignore the Owners Manual, then claim that WE, whom religiously follow the same manual, aren't.

 

Please, do tell me exactly how am I ignoring the owner's manual? I run premium gas, unlike you who runs 87 even though it clearly says 93 is recommended in big bold type in the manual. I change my oil according to the oil life monitor (so far sooner actually, as I've done three oil changes in 8700 miles), unlike you who hasn't done a single one and thinks it'll go 25,000 miles. You are so delusional that it's not funny anymore. I think you need to seek help for whatever problem it is that you have.

 

 

That's why they call you delusional PattyFruitcake! Lol! You just make up stuff the Owners Manual doesnt advise. It says nothing of what you're writing. You should seek help for your inexplicable misquoting of GM and outright falsehoods. Reading is fundamental!

 

I assume everyone knows how varying grades of fuels are transported from the refineries to the distributors, but here's a refresher...

http://www.refinerlink.com/blog/pipe...oducts_to_pump

they are shipped together through the same pipeline in batches that flow next to either without physical separation.

"the example above, the two gasoline products are shipped next to each other since they are very similar in specs. It is very easy to blend 93 Octane into 87 Octane product, so pipeline shippers can put the interface layer between these two products into the same tank as the less stringent product - in this case it is 87 Octane Gasoline"

your fuel may not be perfectly the octane you believe it to be

 

Actually you're the only one that calls me that, and how old are you, 13? And I ask you again, exactly what in the owner's manual am I ignoring? You still haven't explained that at all, because it's fake news. I am not misquoting the manual at all, I have it right in front of me and if I could attach pictures I would (but this forum is acting wonky when it comes to attaching pictures lately) It clearly says in big bold lettering that 93 octane is recommended. And it also clearly says to change the oil according to the oil life monitor and that it must be changed at least once per year. I am following those guidelines, but you clearly aren't. So once again, what am I doing that is against what the owner's manual says? I'm still waiting

 

If you read the article carefully, you will note that the 93 Octane will be the level of Octane that is expected. The 87 Octane may be slightly higher in Octane because it receives the "Transmix".

 

^^^

Hmm, the pipline is filling large storage tanks. The amount of "transmix" would generally be very very small in the 87 tank. Don't count on any extra octane!

 

"87 octane is approved AND recommended for the LT1." - Straight out of the 2017 Corvette Owners Manual. Paying .50 cents a Gallon or more per gallon for a higher octane is a waste of your money.

 

copy and pasted from the '17 OM p.22:

"Use premium 93 octane unleaded gasoline in your vehicle. Unleaded gasoline with an octane rating as low as 87 may be used, but it will reduce performance and fuel economy."

​​​​​I don't think it gets much clearer than that. Use premium gas.

It goes into more detail starting on p.213, but basically saying the same thing with a warning that using a lower (than 93 octane) rating could very well damage your engine.

 

Exactly WHERE is 87 octane NOT recommended AND approved?

 

What page did you get "87 octane is approved AND recommended for the LT1"? Is that a direct quote or a paraphrase with quotes?

 

It's a direct quote of their sentence. If you have a problem with what GM recommends AND approves in their 2017 Corvette Owners Manual, would suggest you take it up directly with GM.

 

What page? Still waiting.

Also, don't confuse "recommended" and "approved." They are two different things. Nowhere that I can find are the two found in the manner you "quoted."

 

Please show me where it is Recommended. No where does it say 87 is recommended. It does say it can be used. That is not the same as recommended. Try reading comprehension. Read the manual below. Does not say 87 is recommended. In fact it warns the 87 will have reduced acceleration.

Page 206 of the 2018 manual states exactly this, as it is copied right out of the PDF manual.

The bold is what they recommend you use for best economy and performance.

The Red can be used, but it will lead to reduced acceleration and fuel economy.

So why would some one buy a High performance car, and be satisfied with not getting the best performance by using a 87 octane fuel?

Sad some one will spend 60K or so on a performance car, and not want the best performance.

 

This was in the manual for a 2016.
If equipped with the LT1 engine, use
premium unleaded gasoline meeting
ASTM specification D4814 with a
posted octane rating of 91 or higher.
Regular unleaded gasoline rated at87 octane or higher can be used,
but acceleration and fuel economy
will be reduced, and an audible
knocking noise may be heard. If this
occurs, use a gasoline rated at
91 octane or higher as soon as
possible. Otherwise, the engine
could be damaged. If heavy
knocking is heard when using
gasoline with a 91 octane rating or
higher, the engine needs service.

 

Not defending the use of 87 octane as I would not use it BUT if you "never" put your foot past half throttle, especially important at lower rpm, the 91 or 93 octane is not needed!

However if you do use 87 octane, one of the many knock sensors will detect a "knock" (preignition) and the computer will retard timing and probably richen the air/fuel mixture in attempt to eliminate it! As the owner's manual states that will reduce max power and reduce mpg. The high octane rating is needed when cylinder pressures are near max based on the compression ratio. At part throttle, the air/fuel mixture does not reach max pressure on the compression stroke and therefore won't preignite or "knock." It's like having a lower compression engine. Unlike a diesel, combustion will (should) occur only when the spark plug fires.

Once the computer sets the timing back and/or richens the air/fuel mixture you're not only loosing max power your getting less mpg! Defeating the $/gallon savings you thought you were getting. Perhaps at every start it looks for a knock sensor signal- don't know. New engines have many knock sensors so doubt you'll hear a knock before it does it's reduced timing etc thing!

SIDE BAR
The statement, "if you hear knocking" remines me of a friend who had a high performance car and traveled to Mexico were he filled up and the car knocked so bad no matter how he drove he was worried he was damaging the engine and probably was. Timing and rich air/fuel ratios can only help so much then it will knock!

Also recall some years ago when my communications manager and good friend got a great deal on a new Olds and when he got it home realized it said use only high test gas. It came with a turbocharger! He said he refused to pay for high test gas so always used regular. Told him the same, just never use more than half throttle! He was not an aggressive driver and probably never did. He had the car for many years and all was fine. Particularly with a turbo charger the max octane requirement is needed when on boost.