Possible new bad gas. What should I do?

[Seachaser]

We have one station that sells ethanol free gas. I’ve been using it in everything for the past 10 years and never had a problem. But I got a bad batch in Florida once in my boat. I had to drain the fuel filter every few days of water until it was gone. It would shut down my two stroke if the fuel filter got full. It’s an easy check.

 

[lone wolf]

Last year I used approximately 9 gallons of fuel with one saw (261). This year I added the other two saws and will cut more wood so I will probably use a little more. I would guess 12-15 gallons a year on firewood. Plus I have my other 2 cycle yard equipment I run for about 9 months out of the year.

I haven’t seen the VP cans locally. I see them on the internet and it looks like a cheaper option.
The Stihl 1 gallon cans are $40. That would add up.
Lowes and Home Depot have tru fuel but I certainly wouldn’t trust that. With their relaxed return policy, I wouldn’t put it past a scumbag to refill the can with old gas and return the gas for a refund.
I honestly wish these cans were sealed when you bought them so you know exactly what you’re getting.

You should be able to get 5 gallons of VP for around 100.00-120.00

 

[OM617YOTA]

You should be able to get 5 gallons of VP for around 100.00-120.00

Just burn TruFuel at that point.

 

[Sidecarflip]

I didn’t know there was such a difference between the summer and winter blend of gasoline. Makes sense now.

Big difference and I can see it in the mileage I get in my buggy as well. In the winter I drop about 5 mpg from 40-35 on the average.

 

[Sidecarflip]

For me being an occasional user, running canned gas makes perfect sense. For someone that isn't, not so much.

 

[bwalker]

Big difference and I can see it in the mileage I get in my buggy as well. In the winter I drop about 5 mpg from 40-35 on the average.

That's not caused by the gasoline. It's caused by the increase in air density that cold brings. More 02 requires more fuel to combust properly.

 

[Sidecarflip]

Sounds good to me but the engine is fuel injected and turbocharged so I'm not at all sure. All I know is it consistently does that every winter. I have a 320 horsepower roller skate, Focus RS turbo.

 

[bwalker]

Sounds good to me but the engine is fuel injected and turbocharged so I'm not at all sure. All I know is it consistently does that every winter. I have a 320 horsepower roller skate, Focus RS turbo.

It doesn't matter if the engine is fuel injected. It's still seeing denser air, the 02 sensor detects how much 02 is in the exhaust and the fuel injection compensates based on this.

 

[OM617YOTA]

Does the density or BTU/gal of gasoline change between seasons?

 

[Sidecarflip]

It doesn't matter if the engine is fuel injected. It's still seeing denser air, the 02 sensor detects how much 02 is in the exhaust and the fuel injection compensates based on this.

I believe you. 35 ain't bad but I do like 40 better. Only car I've ever owned that can go from 0-120 on a freeway on ramp...lol I rarely drive it hard anyway, hell, I'm a 74 year old, old fart. When I bought it, first thing I did was take off all the graphics tape because it's a police magnet. My wife said I was nuts but here in Michigan, it insures as a 'station wagon. economy car, IOW cheap insurance for a supercar. If I have to pass someone, I just drop a gear or 2 and mash it. It has a 6 speed manual in it. Never worry about it getting stolen because car thief's today cannot drive a standard, all they know is PRNDL. Too bad Fords quit making them, it's a fun car. Very comfortable too. Has Recaro front bucket seats.

 

[Sidecarflip]

We have one station that sells ethanol free gas. I’ve been using it in everything for the past 10 years and never had a problem. But I got a bad batch in Florida once in my boat. I had to drain the fuel filter every few days of water until it was gone. It would shut down my two stroke if the fuel filter got full. It’s an easy check.

I run Racor's on my farm tractors and my diesel lawnmower as well. I see they make a Racor for gas engines as well. Great filters.

 

[bwalker]

Does the density or BTU/gal of gasoline change between seasons?

Yes, any time you change RVP you also change density although it's a seldom 1-1 change.
Density actually changes daily to be honest.
For instance if diesel margin is high and gasoline low like it has been we slump alot of gasoline range material down the column that's cut as diesel. The opposite can also happen.

 

[KG441c]

Yes, any time you change RVP you also change density although it's a seldom 1-1 change.
Density actually changes daily to be honest.
For instance if diesel margin is high and gasoline low like it has been we slump alot of gasoline range material down the column that's cut as diesel. The opposite can also happen.

I threw my camshaft pin worn housing Stihl BR600 behind the shop and bought a Husqvarna 570 around 4 yrs ago. Not the 1st issue with the Husky but I had constant issues with the 4 mix. Not a fan of the 4 mix but I work on them daily

 

[Seachaser]

OP, you checked your gas yet. Always eliminate the easiest first.

 

[bwalker]

I threw my camshaft pin worn housing Stihl BR600 behind the shop and bought a Husqvarna 570 around 4 yrs ago. Not the 1st issue with the Husky but I had constant issues with the 4 mix. Not a fan of the 4 mix but I work on them daily

The 4mix is just a compromised design. Some guys get good service out of them. Many do not.

 

[stihltech]

WOW! Three pages of could be's.
How to diagnose.
Clear glass quart jar is one of the best tools in a shop. Shows you cleanliness and water in fuel in a minute.
Anybody read the owners manual. Minimum 89 octane. What oil to mix? Any major brang for AIR cooled motors.
Isn't non ethanol the cure? Only if it doesn't have water in it. I find just as much water in both.
Is there winter fuel. If it gets cold in your area, absolutely.
My advice, no more fuel than you can use in 90 days. Fuel sitting in any container that is not completely closed will make water.
Just saying what we see in a shop daily.

 

[thenne1713]

I had three saws that would not run yesterday after refilling the fuel tanks. I am wondering if I got bad gas. How would I tell if so? How would I prove bad gas? And I am looking for advice. Any way to test the gas?

Saws are Stihl, MS 261 CM, MS 400 CM, and a MS 500i with a manufacturer recommendation of running 50:1 fuel mix.

I would like to be thorough and explain all events leading up to my three saws quit running. This will be long winded but I want all the information given to you so I can get good replies that are helpful because maybe I am over looking something on my part and will be obvious to others.
I use non ethanol 91 octane gas for my saw. Only one station in town sells premium ethanol free fuel. I wanted fresh gas before cutting my firewood for the year.
On Friday 03/01/2024, I go by the gas station that sells the premium 91 octane ethanol free fuel to buy gas for my small engines.
They have a dedicated line/hose for the non ethanol gas but I still pump one gallon into my vehicle since they sell both 87 and 91 octane of non ethanol gas and I want to make sure I’m getting gas pumped from the 91 tank into my gas cans. Basically clear out the “old” gas from the hose. Vehicle tank is 75% full and I pumped in one gallon of fuel.
I have a 5 gallon gas tank and I add red armor 2 cycle oil into the gas can. 3.2 oz of oil per gallon of gas. I measured three “servings” of the proper oil amounts from the 16 oz container and pour it into the gas can. Total oil amount was the 9.4 ozs. I am very cautious as to mix the appropriate amount of oil to the gas can. I add 3.1 gallons of gas (pump reads 4.1 gallons because I added the one gallon to my jeep). With the fuel and amount of oil I added this should give me right at a 40:1 mix.

Next I have a VP racing fuel can that holds 6 gallons. I put close to 6 gallons of fuel into this can per the reading on the fuel pump. This leaves quite a bit extra room at the top with air which I am fine with because I don’t want any spills in my jeep.
I noticed the gas cans seemed “low” after “filling them” I had 3.1 gallons in a 5 gallon fuel can (only used for mixed gas and this was empty when I put the fresh gas in it). So common sense, I would think it would be over 1/2 full. I know the gas can can hold more more than it’s listed because manufacturers leave room for air. But this was less than half full. Then the VP fuel can has markings on the plastic with graduates gallon markers. This was showing a hair over 5 gallons and I almost put 6 gallons in it per the gas pump. So this did raise an eyebrow but then again I questioned how accurate these markings are on the fuels cans. No way to be sure if I received the correct amount of gas but I figured the gas station pump is calibrated and is dispensing the correct amount of gas and the plastic fuel container reading on the side isn’t accurate so I pretty much blew it off. Those plastic containers do swell a little in the summer so I told myself the reading on the cans probably aren’t accurate.

So now Sunday I go to cut wood. The three saws have gas in them from the last time I used them. The fuel level in the tanks are ranging from 3/4+ of a tank to 1/2 full so I top all three off with the new gas. They run fine. No problems.
The 261 runs out of fuel first and I refuel. I only have mixed fuel on site and I am very cautious not to straight gas the chainsaws. I personally am the one to fuel the saws. The 261 gets a full tank of new fuel, and I top off the other 2. The 400 gets about half tank of fresh fuel (it originally had the most full tank to begin with, so it received the least of the new/fresh fuel on the first fill before starting). The 500 was about 3/4 empty so I topped it off again with the fresh fuel.

I start the 261 and a buddy is cutting with it. I’m taking a break and I noticed after a few minutes, it starts running rough and dies. He restarts it and it will barely stay running. He says something and I say something about the large temperature change throughout the day. It’s now 80 degrees outside and maybe the m tronic needs to be recalibrated. I recalibrate it and the saw is running better but not great. It runs for another few minutes for him to make made 5 cuts or so but isn’t running great. So I say let’s dump the fuel and re fill it since the first thing in my mind is maybe some saw dust got in the tank. I checked and tank was clean. I noticed when I opened the fuel cap on the chainsaw it was under a vacuum and I could hear the air sucking into the gas tank as I went to open it. The fuel was bubbling from the fuel filter. I dumped the fuel from the tank even though the inside of the tank was clean and I refilled the 261. The saw started and idled for 2-3 seconds then would die. If I tried to blip the throttle the saw died instantly.

I set the 261 to the side and tell him to use the 400 and I’ll see what’s wrong with the 261 when I get back home. He starts the 400 and begins cutting. I proceeded to start the 500i now that it’s been refueled and it will start and idle for about 1 second then die. I try several times With the same results. I can’t try the throttle because it dies too quickly. I started the saw 7-8 times, it would idle for just a second and die. So the 9th is so time after trying to start it, the 500 would not even start.
He noticed me having problems with the 500 and shuts off the 400 and says he doesn’t think the 400 is running like it did before re fueling.
We come to the conclusion that the only common denominator between the three saws is the gas. We go to the local ace hardware and buy a gallon of canned fuel. They only carried tru fuel. I bought one can of tru fuel 50:1 mix. Once back on site, I emptied the tanks of the gas out of all three saws and added the tru fuel to the tanks.
All three saws started with just a few pulls. All three saws ran just fine after that and didn’t have any other problems.

I still have the gas from the gas station, both the mixed gas and the regular gas. I kept it in case it damaged my saws or needs testing.
The vehicle ran fine with no issues but that one gallon was mixed with 15+ gallons of gas that was already in the tank.

I was concerned when I got home about the gas damaging the cylinder or piston on the saws. I pulled the mufflers on the 261 and 400. Looking through the exhaust port, the front of the piston looks great with no marks. I lowered the piston and was looking at the back cylinder wall and I think I see something. It looks the same on both saws. The cylinder is shinny in a few spots on the back and I *might* be able to see two vertices lines. I was reading on here about bad gas damaging the back of the cylinder and piston on the intake side. I was looking at the technical bulletins from stihl and echo diagnosing damaged pistons and these lines on my saws look nothing like the scoring on those pictures. It’s hard for me to tell if I have damage or just normal wear and I can’t get a decent picture with my phone and lighting.

Does this sound like bad gas? If it damaged the saws, would they even be running? I don’t has a compression tester but the saws did seem to run fine after using the tru fuel. No, these saws were not straight gassed.
Another thought I had was if I was “shorted” on the gas and I was mixing it at 40:1 to gain extra lubrication and the manufacturer only recommends a 50:1 mix, and I received less gas than what was shown to be dispensed then could there have been too much oil for the saws to run?
I might be over thinking this and concerned over nothing but if the gas station sold bad gas and damaged my saws, I would want them repaired. Would it be obvious if the saws were damaged and would I be able to see this damage through the exhaust port? Or would the saws need to be taken apart? Any advice would certainly be appreciated.

Edited to add: I noticed the gas bubbling in the chainsaw fuel tank. The bubbles were coming from the fuel filter in the tank. Not sure if the tank was pressurized or under vacuum but I could hear the hiss of air when popping the fuel cap on the chainsaw.

I wud not be concerned about damage as much as disposal, as sounds like something I wud not want to add to the car/ truck tanks either? It should do not more damage than "running out of fuel"? I encountered similar/ worse when a neighbor borrowed my tiller and cud not get to run.

 

[OM617YOTA]

Yes, any time you change RVP you also change density although it's a seldom 1-1 change.
Density actually changes daily to be honest.
For instance if diesel margin is high and gasoline low like it has been we slump alot of gasoline range material down the column that's cut as diesel. The opposite can also happen.

My thought was that less dense fuel in the winter would give lower mpg. I doubt it would cause more than a few percentage points difference, not 5mpg in a 35-40mpg car.

For @Sidecarflip the mpg difference is likely more due to colder temps causing the engine to take longer to get to full operating temp, and running in the less efficient open loop mode longer. Also, cooler denser air makes turbo engines happy, when the air going into the turbo is cooler, the air coming out is cooler, and the intercooler also works more effectively. All that means more air going into the engine, so more fuel has to be burned to maintain the programmed air/fuel ratio, impacting mpg. More power, though. Are you measuring mpg by doing calculations at the pump, using the car's computer, or just seat of pants?

 

[OM617YOTA]

I wud not be concerned about damage as much as disposal, as sounds like something I wud not want to add to the car/ truck tanks either? It should do not more damage than "running out of fuel"? I encountered similar/ worse when a neighbor borrowed my tiller and cud not get to run.

A slow running water cooled engine with modern fuel injection is an entirely different beast from an aircooled chainsaw, even if Mtronic. Plus the fuel would be dilluted in gallons of non-suspect fuel. I'd run it myself and not worry.

 

[bwalker]

I wud not be concerned about damage as much as disposal, as sounds like something I wud not want to add to the car/ truck tanks either? It should do not more damage than "running out of fuel"? I encountered similar/ worse when a neighbor borrowed my tiller and cud not get to run.

Modern fuel injected vehicles digest bad gas just fine.
That's assuming the gas in question is bad. I bet there is nothing wrong with it other than the RVP not being suited to warm weather.