2kwik4u

The problem with these types of statements is that most people don't understand modern engine control systems. More often than not there are advanced sensing algorithms, and active feedback control loops that can and will allow advanced ignition timing settings. So simply saying "Higher octane doesn't do anything" is incorrect. Even adding "than what your engine was designed for" isn't really correct, since it was designed to run on ALL fuels not just ONE fuel. Without intimate knowledge of the control system, the only way to tell if a higher octane fuel will improve the situation is by experimentation. My '12 Focus reacted quickly and significantly. My wifes '10 Traverse had no reaction at all. My Sierra has a subtle reaction.

I think this is hte exact case. I've been watching the data on timing and knock retard on my truck for a few weeks. I don't have good longs to backup my anecdotal thoughts here.....HOWEVER.....it appears that running on 93 nets me less overall time with knock retard in effect. Leading me to believe the timing parameters are setup such that they are purposefully advanced, and letting the knock sensor report problems and adjust on the fly. This would lead to a "constantly optimized" condition where the truck was always running as much timing as practical, without undue risk of damage. SO.....When moving to 93, you spend less time with timing retarded and see a net overall gain. Again, though, the gain is small. Very small. Just enough to offset the difference in the cost of the fuel on a per mile basis it appears. Defintiely not enough to feel in the seat of the pants, or hear in the ping of the engine.

I've always tried to start this in the spring time, right when it warms up and the providers have moved to summer blend. I'll do basically the procedure you mention. Run it pretty dry, swap to next octane on the list, run a tank, and refill. Then start data collection. This is the first vehicle I've had that didn't show a marked difference in $/mi. Even my '03 Yukon had a difference of $0.015/mi. While these are still just pennies per mile differences. Over the course of a 100,000 miles, that's $1,500 in fuel. Might be negligible to some, but seems worthwhile to me. I should also mention I've had a few vehicles where the choice was made for me (Audi A4 with mild tune, and Silverado SS with a rebuilt engine) to run 93. I've also found the opposite to be true where 87 has been the least expensive, for instance, wifes '10 Traverse also gave zero craps about octane, always returned nearly the same cost per mile, and had no noticeable driving benefits to one fuel or the other. We ran 87 in that one.

I want to take a second and elaborate on this portion of the EXCELLENT post above. I do the following for every vehicle I've owned since my '00 S10 (like 7 of them now I think)......Drive for a month on each of the fuels your vehicle can accept. For instance, I had a '12 Focus Se. It would accept 87, 89, 93, and E85. After driving each fuel for a month I computed the dollars spent per mile driven for each fuel. Turns our 87 octane was the MOST expensive fuel I could be using. Followed by 89, E85, and 93. The E85 and the 93 were within fractions of a cent of each other ($0.115 and $0.118 per mile). This was based on a the cost of E85 being around $2/gal, and 93 around $3.75/gal. In the end, I ran 93 in that car with great results. I'm in the process of testing my current truck. Been running 93 Octane for almost a full month now after trying 87, and 89. So far the results are far less dramatic than with other cars. Each fuel is netting me REALLY close to $0.175/mi. 87 was $0.172/mi and 93 is currently at $0.178/mi. The 93 however runs SIGNIFICANTLY smoother in a subjective "feel" assessment. I'm most likely going to continue with the 93 when I complete the test based on that feel alone. Considering the price is so near the same on a per mile basis. The assumption here is that the factory tune was running with some level of knock retard on the 87 at all times. With the 93 it is allowing itself to "trim" the timing higher, make a few more hp, and offset the added cost of the premium fuel. Obviously it's on the order of fractions of a HP considering the relative cost per mile is SOOOO close. Moral of the story....don't just say 87 is the cheapest and let it be. There is a decent chance a higher octane/blend will be less expensive, and (at least in my particular case), it might be a wash in terms of cost, but a win in terms of driving feel. Data is your friend, and follow it's trends more than any placebo effect you might get.

Thanks for the welcome, and the vote for some monotubes. Been lurking for 18mo or so. Just recently started being more active here.

I was thinking some more about this on the way into work this morning (we were out of coffee and I had to do something to keep my mind busy for 40 minutes)...... The best explanation I could come up with between the two trucks I drove is that my personal truck ('15 SLT Z71) is very "nervous" over bumps, while the loaner truck ('18 LT Z71) was very "composed" over most bumps. For example.....There is a left hand sweeping curve on the expressway in the morning. Large pothole on the left side of the lane right in the middle of the curve. It's got a "sharp" edge on it, is about the size of a frying pan, and is 1-layer of concrete deep. City has fixed it multiple times and it keeps coming back. My truck hits that and it hits hard. I can feel it in the seat, and steering wheel. The front and back end scoot over a shade, and the whole truck feels largely unsettled. The loaner truck would take that bump in stride. It wasn't as much of a "bang" as it was a "thud" in the feeling. It was general softer overall, and the truck remained mostly settled throughout the impact. The constant "banging" and "nervousness" of my truck is what I'm looking to eliminate. I want a nice "composed" ride. I want it to take the hits, but continue on it's intended path, and reduce some of the impact into the cab. The plan is to find some softer sidewalled tires, and a new set of shocks and see where that gets me.

Same here. Same assumption. Drove my 73k mile '15 SLT Plus into the shop, and was handed the keys to a '18 Silverado LT Z71 with 3.1k miles. Both had the factory ranchos. My truck has the 20in wheels, the Silverado had the 18in wheels. The 2018 truck drove SIGNIFICANTLY better than mine. I'm suspecting my stock Ranchos are long past their "replace me" time. Combined with the stiffer sidewall of my 20in KO2's, and the assumed faulty shocks, my truck rides like a hay wagon. Bounces badly on large undulating rises, and does little damping on sharp square edge bumps. It's a very harsh ride overall, and somewhat "floaty" in all scenarios. The Silverado was well composed over the same roads. Small bumps went away, and large rise/falls were not "bouncy" or "floaty" at all. It was seriously like I had two completely chassis's underneath them. The Silverado had a bit less damping overall than I would have preffered, but I'm unsure if that was the large sidewall tires, or the shocks. I'll be swapping over to Bilstien 5100's (on stock height settings) within the month. I'm also on the search path for some taller sidewall tires in a P series instead of the LT series. Love the look of the KO2's, but they're noticeably heavier than the stockers,, and ride like they're almost solid. Handle nice and have lots of traction though.

Thanks for the response. My stock Ranchos are spent at 75k miles, and I defintely need something else. The 2018 Silverado the dealership put me in as a loaner has Rancho's and is equally as "floaty" so I think it's not just worn shocks, but poor valving choice on GM's part. My truck has the KO2's (275/55/20) on it now. They were on it when I bought it at 36k miles, and they are wearing well. They are loud on the road, and stiff as hell sidewalls (they're an LT, not a P tire). I LOVE the look of them, but don't really need the capability they afford. Looking to move back into a P rated tire with slightly less aggressive tread on the next set. The WildPeaks have been on my radar as well as the Continentals. I'm considering adding a bit of sidewall as well to help with the ride. Thinking maybe a 275/60/20. Haven't really gotten that far in research yet though. Thanks again for the response!

How do you like the ride with the level? I'm |..| that close to pulling the trigger on some new Bilstien 5100 shocks, and some new taller sidewall tires (looking at Continentals in the same size you have). My truck currently rides worse than a covered wagon, and the '18 Z71 they gave me as a loaner is much better. Hoping it's just shocks and sidewall difference, and not something else.

Thought I had a lot on my '15. Just turned over 68.5k this weekend. Bought it with 36k 16mo ago, so I'm sure I'll be into the 100's in no time. Hoping to keep this one to the 10yr mark. Would put me just over 264k miles if I keep at the 2.2k mi/mo pace I'm going at now. Kept my '03 Yukon to 187k before electrical gremlins were taking longer to deal with than I had time to give it. Rest of that truck was still solid though.

Thanks for the compliment. Those are 275/55/20 BFG AT K02 tires. Came on the truck when I bought it. Little stiff and heavy for my liking, but the traction is great, they look amazing, and are wearing very nicely.

Thanks for the replies. This might end up being a "vanity" purchase just for the look of the 5100's. The do certainly look a good bit nicer than the 4600's. Have to see how this tax return thing works out. Wife is already talking new couch. Don't tell her I've already ordered a new bed cover

I do like the look of the 5100's over the 4600's. Local 4WheelParts outlet has both in stock. $279 for the 4600's and $379 for the 5100's. For that little bit extra I'll probably go with the 5100's just for the look. If I had a money tree I'd figure out how to adapt a set of QA1 double adjustable coilovers onto the truck. Had those on a previous vehicle and dialing in the correct rebound and bound damping was awesome. Had multiple "preset's" figured out depending on what I was doing, and was able to adjust to those settings in minutes. Really cool setup, but easily 4 times the cost of some stock replacements.

2015 Sierra SLT. Has damn near every option available. I've heard someone call it an SLT Plus, although not sure what that is. It's a very high optioned Z71 Sierra SLT for certain. Has most of the doo-dads that come on the Denali with the exception of the fancy all glass gages, no MagnaRide, and no 22's. Only option I don't have that I wish I did was the 6.2L, I searched for a month to find a black one with the 6.2 and these options and couldn't find anything within 500 miles (was trading in a TBSS that I travelled to Canada to get, and was a basket case when I got home, so the wife was VERY against me travelling to get another vehicle). This one was about 100 miles away and checked all but one box, so I brought it home. Given me about 25k miles of trouble free service so far in the 16 or so months I've had it.

Awesome. Thanks for that. Now off to search for a set!

Looking ahead to warmer times......winter is dumb, come on spring!

Does anyone have the 5100 shocks and have them set on the "stock" setting? I have no desire to level or raise the truck at all. I have a strong desire to dump the POS Rancho shocks that are entirely too stiff for this vehicle.

That does look nice.

WOW, great review. Thanks so much for the info. I really prefer the look of a soft cover over a hard cover, but it's difficult to find. I think the Sentry CT might be top of my list now. Thanks again!

Dangit should've checked the site yesterday.... $90 Front and $97 Rear now........

How do you like the the fabric on the CT? I like the look myself, curious how it holds up to dirt/debris and cleaning. Any thoughts?

I feel like there is a "That's what she said" joke in there somewhere. And yeap, same 2kwik4u from SSF. Still post over there once a month or so. Only about 6 of us left that are actually active though

Thanks for the info. Looks like the 5100 are the way I'm going to head. Hoping for a year end blowout sale from somewhere to pick them up from. Anyone have a recommended dealer/shop to purchase from?

How old were they when you replaced? I'm sitting at ~63.5k miles right now and I've put the last 30k miles on the truck with little change in the ride/handling that I can tell. Wondering if mine were busted when I got it?

Running the factory 10-spoke 20" wheels that came on it. Here's a pic from the day I bought it. Not a great picture, but the only one I have on my office PC.