? about HP numbers on 91 and 87 octane

[windsurfnut]

Looking at a tuner for a 2017 Silverado 6.2

91+ tune says + 20hp
87 tune says +13hp

For my question, lets assume just for the use of this exercise that the motor makes the advertised 420hp and that the tunes add the stated amounts directly to peak output.
91+ tune would add 20 hp for a total of 440hp

is the +13hp on the 87 tune then net a total 433hp?
OR
is the +13 hp based on what the 6.2 would produce after pulling timing/adding fuel when 87 is detected. So again, for this argument the computer reduces the motors output lets say 10% or 42hp from the normal 420hp when it detects knock/lower octane fuel. 420-10% (42) = 378hp.
add back in the +13 hp for the 87 tune and the net is 391hp

Follow my questions logic?

My question is really regarding running the 6.2 on 87 and the expectation over what the stock tune would do with either 91 or 87 octane.
Thanks!

[06MonteSS]

With that 6.2, you need to use at least 91 octane gas, so make sure you are using GOOD 91/93 octane gas, it makes a difference... mobil, exxon, sunoco, amoco, bp, chevron are best brands to use, with mobil and exxon being the best..

NEVER use Shell, costco/bj's, mom-n-pop, or no-name brands, as it's crap gas that tends to cause a lot of knock retard and less performance/mpg...

so you would use the Diablo Tune - that's the 91/93 octane tune...

[windsurfnut]

Thanks for the reply, but that did not address my question.
There is an 87 tune option for the 6.2, correct?
How are the HP gains calculate on the 87 tune? From a stock tune running 91 or a stock tune running 87 where the timing has already been pulled back by the ecu?
Thanks

[06MonteSS]

there is an 87 tune listed, but you don't want to use that on that 6.2 engine.. it's listed for all trucks, no matter which engine it has in it.. but you want to use 91/93 octane gas in that 6.2 truck and the Diablo Tune..

hp/tq numbers are from the tunes compared to stock.

[windsurfnut]

Thanks.

Can you elaborate on that?
If I wanted to run 87 octane in the truck, with your 87 tune, could I do that and still achieve close to stock or better MPG.

I have not purchased the truck yet, and I would like the option of running 87 and maintaining good mpg and have the option to run 91+.