I want to add additives to the fuel in our vehicle

[45ACP]

I am wanting to add additives to the fuel in the GMC Envoy. (03, Envoy XL, has the big six-cyl.) I am torn between Seafoam in its recommended dose, MMO, and Chevron. Of the three, MMO is the cheapest but may do the least cleaning.. Seafoam is a favorite, works well.. and Techron is the most expensive. The desire is to 1. Clean up fuel system as this truck has been somewhat abused but is holding up, want to keep it that way and 2. Maybe it will begin to do something about the "cold carbon knock." i suspect carbon in engine.

We use low-quality "no name" 87-grade fuel EXCLUSIVELY due to cost, its literally the difference between $3.51 a gallon and $3.79 a gallon.

Which of the three would you choose? Thanks.

 

[demarpaint]

I'd use Techron first to clean the system. Then use MMO @ 4 ounces/10 gallons of fuel at each fill up. The Techron will clean the system, the MMO will do some light cleaning after the Techron, act as a UCL, and keep the system clean.

 

[david_ES2]

Out of the 3 id use chevron techron but id use redline sl1 before either of those unless its not.readily available for purchase where you live.

 

[SnPb]

I have an 03 Trailblazer with the same engine that developed a piston slap sound at about 70K miles. It sounded like a diesel on a cold morning. I read about the carbon deposit issue and used a few bottles of Chevron Techron. It didn't improve overnight, but it is pretty quiet now at 121K miles. I also started buying gas from Quik Trip when they opened some stations in the area, as opposed to from the least expensive station. The Quik Trip's are usually among the lowest anyway. I think that O'Reilly's has a two for one deal right now on Techron.

 

[BMWTurboDzl]

Do some easy cost benefit analysis between "no name" fuel with Techron and name brand fuel only.

 

[HerrStig]

Why do it unless you have solid technical grounds for it.

 

[ARCOgraphite]

Use better fuel over adds. Up here good luck - there aint any. You can always get some Xylene or Toluene at the hardware store.

 

[barlowc]

You might want to consider Gumout Regane too.

 

[Oregoonian]

2nd....Either RedLine Si-1(if you can gey it)... or Chevron Techron.

After that....MMO every fill-up (3 to 4 oz per 10 gal.)

 

[Vikas]

Since this is not your vehicle and you do not drive this daily, it is a perfect one for you to do a blind study. Select Techron or Redline or Regane and put it in but do not tell the primary driver. If it were to make a difference, she will tell you on her own.

 

[hardcore302]

Redline as a first dose, then mmo as maintenance dose.

 

[45ACP]

Cool. BLIND STUDY!!! I like that. it is my goal to clean it up as much as i can.. without messing it up.

Vehicle: 2003 GMC Envoy XL, the six-cylinder.
Start mileage: 146,670 (this thing does get 1000+ miles every week! Everytime i look its up)
Symptoms: original fuel filter, maintenance not possible, exclusive use of poor quality cheap gas and questionable oil. Sludge condition unknown. Overcooled for one year, ~20,000 miles + more like 40 to 50,000 miles+

Exhibits cold carbon knock, to varying degrees.

I WENT TO WALMART We all know I overpaid on oil tyday.

I put 16oz MMO and maybe 3oz Seafoam in the OIL (its not 10W-40 anymore.)

As to the gas? .. well, as soon as I can ill put the 4 ounces NOT THE WHOLE BOTTLE in. e are at 3/4 tank, was full yesterday...

In the last 1000 (2000?) miles I have put in a full can of Seafoam and a bottle of Techron. Mighta been two cans Seafoam.. but that was at the same time and back when the engine was overcooled. I opened the hood and added what i said. Nothing in the gas yet.

WM has MMO and Seafoam. No Gumout or Lucas or stuff like that or anything else.

And if they had Redline SI-1 id get it.

Now, what will be the result of the MMO and itty bitty Seafoam in the oil? Cleaning? UCL?

 

[gathermewool]

It's not carbon causing that knocking sound...

I'd stick with a proven cleaner like Redline SI-1, Techron, or Gumout w/ Regane. I've used every product mentions so far in this thread and notice no differences. Even on the 97 Legacy with over 200kmi, there were no issues, though I mostly used Shell and Mobil in everything I drive.

Regardless, if people ask for my opinion and cost is the issue, I say not to use ANY products unless there's some symptom needing resolving. Saving $3-$4/tank using "[censored]" gas only to worry about using additives doesn't make sense to me. Beyond that, adding a product for use as an UCL makes even less sense to me on a modern vehicle. It's the conjecture that promotes the use of these additives mostly, and they're mostly not beneficial.

JMO, but I'd suggest you keep doing what you're doing. The noise you hear on cold startup could also be lifter-related or piston slap.

 

[daves66nova]

Originally Posted By: 45ACP
Overcooled for one year
OVERcooled???

 

[MrRPM]

Originally Posted By: daves66nova
Originally Posted By: 45ACP
Overcooled for one year
OVERcooled???


The thermostat was stuck open, resulting in the car never really warming up.

45ACP, why did you add MMO AND seafoam to the oil together?

 

[wkcars]

Techron isn't too expensive if you get them when it's BOGO, like right now at oreilly, $7.99 for the 12oz bottle ($4 each bottle) or $12.49 for the 20oz ($6.25 each bottle).

 

[45ACP]

Originally Posted By: MrRPM
Originally Posted By: daves66nova
Originally Posted By: 45ACP
Overcooled for one year
OVERcooled???


The thermostat was stuck open, resulting in the car never really warming up.

45ACP, why did you add MMO AND seafoam to the oil together?


I only added about 3oz. Seafoam and 16oz. MMO. Did so to 1. Thin oil down from that 10W-40 plus STP fill (we suspect it uses oil) and 2. CLEAN! Something, somewhat, slowly.

I don't even want to think about what the overcooling did..

I see a fellow Trailvoyer here. Same year same engine; we have the XL version of LTZ version of your truck. 146,460+ miles on ours. Could the use of heavy oil be due to the SUV sounding like a Mitsubishi Fuso diesel or Isuzu NPR or MACK TRUCK when it starts?

 

[MrRPM]

seafoam or mmo alone would have thinned your oil and both cleaned well.

be careful not to over fill your oil, by adding all this stuff your adding to the oil and some people don't realize then need to counter act that by taking some oil out.

personally i wonder whats going on in your engine between the bulk 10w-40, stp, MMO, and seafoam. i wonder how much is actually motor oil. lol

 

[morris]

my idea MMO ONLY. check out this out fit http://www.ampcolubes.com/

 

[yonyon]

Originally Posted By: ARCOgraphite
Use better fuel over adds. Up here good luck - there aint any. You can always get some Xylene or Toluene at the hardware store.


I'm curious, what does that mainly do for you? I can see it would probably give a tad higher octane, be water free, and smell nice, but does it do enough of that to justify the price or is there something else?