Will a 8.1 run on 87 octane unleaded or does it require 89 or premium? Thanks

I have learned that in the computer controled engines today what ever octane gas your vehicle was programed for is going to be the best gas to put in. I can't see a GM truck taking anything more then 87 octane but just check your manual and it should tell you. If your engine runs better on a higher octane gasoline other then what it was programed for then there is something wrong which should be fixed rather then band aiding the problem with exspensive gas.

Usually the 8.1L will run better on 87.. However if you are running a programmer there is a setting telling the computer whether you are running 87 or 89. Not sure how much of a difference it will make, just letting you know...

The 8.1L runs (and is spec'd) on RUL, I have run MUL and PUL and saw/felt no difference in pickup or mileage. The only differenece was the absence of the initial hot start single 'knock' when first lit.

DEWFPO

8.1 I had ran great on 87 octane. At high altitude 85 octane worked fine. Gave it one fill on premium by mistake and could not tell any difference.

Truth is if your truck is programmed to run on 87 octane.....and it is if it's stock.....then that is the best grade fuel to run. Running anything higher can result in carbon buildup in the combustion chamber and on related components. Once carbon builds up, hot spots develop and you begin to experience pre-ingnition (pinging). My 96 Caprice LT1 (tuned for 87) was fed a steady diet of premium fuel by the previous owner ( he thought it gave the car more power...doh!) and now its......ping ping ping.
JP
JP

Heartbeat... check the EGR valve on your caprice.. IIRC the LT1 was supposed to run premium, that's what killed some sales at the dealer I used to work for. Peolpe would buy Impalas and have no problem buying premium, they buy Caprice with same engine and gripe about buying premium

Heartbeat... check the EGR valve on your caprice.. IIRC the LT1 was supposed to run premium, that's what killed some sales at the dealer I used to work for. Peolpe would buy Impalas and have no problem buying premium, they buy Caprice with same engine and gripe about buying premium

Nah it's rated for 87 octane even the Impala SS is 87 octane.....and I did replace the EGR valve, O2 sensors, cap & rotor. Some say to get it MOTORVACed, but no one in the area does it. Thaks for the insight though.

Heartbeat Hauler.... A stock or modified LT1 for that matter, should not "ping" if it is mechanically sound. The knock sensor should detect detonation before the huuman ear hears the it and begin to pull timing. I suggest getting a datalogger and check to see when and if knock is being detected, how much if any timing is being pulled, and if timing is being pulled, when and and at what rate the timing is being re-introduced. Have you tried Sea Foam or similar products to reduce carbon buildup?

Heartbeat Hauler.... A stock or modified LT1 for that matter, should not "ping" if it is mechanically sound. The knock sensor should detect detonation before the huuman ear hears the it and begin to pull timing. I suggest getting a datalogger and check to see when and if knock is being detected, how much if any timing is being pulled, and if timing is being pulled, when and and at what rate the timing is being re-introduced. Have you tried Sea Foam or similar products to reduce carbon buildup?

You are right about a sound LT1 running ok on 87, but like I said I don't think mine is sound....in that I have not found (the mechanic actually) any problems with any of the systems, but probably suffer from carbon buildup. I replaced all the above mentioned stuff just because it was due (100,000 miles). Lots of folks have mentioned the SeaFoam on the ImpalaSS forums, but I'm a little apprehensive about doing this because several guys said they locked the engine up. I don't know if that is actually possible, but the term HydroLocked was bantied about. So I haven't really done anything since the major maint. was done. GM dealer says everything is OK and it is probably just build up in the combustion chambers. So it's a pinging I go. I should note that it doesn't do it all the time....mostly on accelaration or up hills, but it shouldn't do it at all. Knock sensors were also checked and they are OK. When my wife gets back in town I'll ask her if I can have my balls back and I'll try the SeaFoam....:D
JP

Using LT1 Edit I played with my 94 z28's timing tables and increased my advance to 36ish deg from off idle throughout the rpm range and the knock sensor(LT4 type) still did not detect any spark knock. The knock sensor detects detenation long before you can hear it ping and that's why a datalogger is essential to see exactly what conditions are present when the knock occurs and how much the timing is being retarded at that instant. If you are hearing a ping that means the knock sensor is not able to pull enough timing out fast enough or it is not detecting the knock. How did the dealer test the knock sensor? Is the car stock? What do the fuel trims and O2 sensors look like? Any opti-spark issues or intake manifold gasket leaks? I would rather trouble shoot a ping than the usual false knock. Fun stuff!

Feed the seafoam in slowly and you shouldn't have any issues. Amsoil makes a product called Power Foam that also works well.

Good luck and get them ballz back before she wants to keep em for herself! :eek:

mine seems to run alot better on 91 octane,but I'm usually at 6200ft and above for most driving conditions

Using LT1 Edit I played with my 94 z28's timing tables and increased my advance to 36ish deg from off idle throughout the rpm range and the knock sensor(LT4 type) still did not detect any spark knock. The knock sensor detects detenation long before you can hear it ping and that's why a datalogger is essential to see exactly what conditions are present when the knock occurs and how much the timing is being retarded at that instant. If you are hearing a ping that means the knock sensor is not able to pull enough timing out fast enough or it is not detecting the knock. How did the dealer test the knock sensor? Is the car stock? What do the fuel trims and O2 sensors look like? Any opti-spark issues or intake manifold gasket leaks? I would rather trouble shoot a ping than the usual false knock. Fun stuff!

Feed the seafoam in slowly and you shouldn't have any issues. Amsoil makes a product called Power Foam that also works well.

Good luck and get them ballz back before she wants to keep em for herself! :eek:

Yikes! Your talkin' greek to me, but to try to answer some questions, the o2 sensors are new, Opti cap & rotor new, plugs & wires new (Jacobs Elec. 8.5mm). As far as how the tech knows the knock sensor is working...I dunno that's what he said and I talked to him not the service writter. I will try the foam thing and realy again it only pings 5% of the time on 87 octane. Some of the guys said to go to the LT4 knock sensors but they are less sensitive than stock (pulls less timing) so that would make the problem worse in my opinion. Yes, the car is stock except for the wires and the K&N filter. I think your scanner idea is a good one. Maybe I can find a mech. that will test drive it with the scanner hooked to it.
JP

I always ran 87 in my 2001 GMC Yukon XL 2500 8.1. Never noticed a difference with premium while driving it.

I own a 1995 Caprice 9C1 (former NCHP cruiser). It has about 106,000 miles on it, and runs very strong. I have never once heard it ping, and mostly I run 87 with a mix of 93 once in awile. It does have a HyperTech tune but I'm not sure if it's the regular gas or premium gas tune. Mainly the HyperTech was used to fix the speedo error after a 3.08 to 3.42 gear swap by the previous owner. Engine is totally stock, including intake and exhaust. Man I love that car! It's my 4 door sports car. Paid $2,000 for it a few months ago. I'm on the www.9c1.net (http://www.9c1.net) forum as Chris 95 9C1. :)

Heartbeat: The motorvac is a machine that uses a pretty good detergent mixed with gas, we use one all the time at our shop. It bypasses the stock fuel system and has it's own internal pump to pressurize the fuel rails. BTW I forgot to ask one BIG question regarding your ping.... what's your coolant temp? Too high will knock like all get out regardless of what you try.

I haven't locked an engine with this machine.... yet. Check motorvac.com

Heartbeat: The motorvac is a machine that uses a pretty good detergent mixed with gas, we use one all the time at our shop. It bypasses the stock fuel system and has it's own internal pump to pressurize the fuel rails. BTW I forgot to ask one BIG question regarding your ping.... what's your coolant temp? Too high will knock like all get out regardless of what you try.

I haven't locked an engine with this machine.... yet. Check motorvac.com

I have checked the website and the closest shop is Louisville, KY, but I called those guys and they don't do it. So I guess the site isn't updated. Not sure about engine temp as I only have the temp guage/idiot light to monitor it. I have thought about trying some Purple Ice in the radiator and see if temp was an issue. I don't remember why, but I think I got talked out of it on the forum ( not this one). I may revisit that option. As far as the engine locking, that was with the SeaFoam and I may do that also. Thanks though.
Jeff