Why would diesel quality change engine sound?

[03TDICommuter]

I usually buy my diesel at Costco as it's the least expensive in town. Last tank though I used a un-manned fuel depot that also caters to semis. Used one of their high flow pumps, filled up to the brim and found their pumps are dishonest. Put in "15.8" gallons that should have been 14.6 (no way I only got 43 MPG on the last tank). I've NEVER put more than 14.9gallons into the bug.

Anyways, afterwards I noticed my Beetle was a LOT noisier when cold. Noticeable so until it warmed up. BUT it also felt peppier, and I'm pretty sure I was seeing it haze at night which it's never done. Best mileage on this tank too in a while (48.6 MPG for 721 miles).

Refilled yesterday morning from Costco. Immediately notice the engine is back to being quiet. Too early to tell what the MPG is as I've only put 200 miles miles on it. I'd also feel like it's back to not being peppy. (I have an underpower problem).

Question for the group - what fuel quality would make the engine noticeable louder clackity wise in the morning, and have a bit more pep?

FWIW, I've gotten bad regular gas from here many many years ago such that I stopped buying RUG there. I usually don't get diesel there as it's inconvenient and usually not cheaper than Costco. Thought their diesel would be okay quality wise, but not so sure now.

 

[burpod]

well btu and cetane likely different. that combined with whatever tune you are running at the moment and the temps - both coolant and air. lots of variables could definitely make a difference. if btu/cetane of one fuel was signifcantly different than another, that would effectively change the timing as spec'd by the tune....

 

[turbodieseldyke]

Used one of their high flow pumps, filled up to the brim and found their pumps are dishonest. Put in "15.8" gallons that should have been 14.6

One time i filled up at a Chevron that gave me "15.7". My previous high was about 15.0, so i wonder if the clicks-to-top is where they ripped me off. I'd expect high flow pumps are even less accurate during the click-offs.

Other guys filling up their 100g fuel cells at that station will have a good idea if they're getting ripped off too.

 

[jettawreck]

Living up in the cold country we get "winterized" fuel starting in Oct/Nov at most fueling locations. Either/and thru additives or blending/both by now most fuel is rated for expected extreme cold (-24*F a few days ago, forecast -34F tomorrow night), however many bulk and/or "truck stop" stations will sell straight #2 and #1. If you are filling up to go where you don't need cold weather fuel you don't buy it. If you want/need cold weather fuel you can either blend your own ratio or use straight #1.
I suspect you get/got some non-winterized fuel at the truck stop and even given your climate the lack of additives and/or blending made the difference. Straight #2 will always give you better power/mileage than "blended" winter fuel up until it is too cold for it to flow, then you realize the error of your ways.
Otherwise you got some sub-standard fuel which I have found to be rare.
Signage on a local station pump.
Wow, adding a pic on this forum is a real long process...
Sorry for the size, don't know how to work that out.

 

[03TDICommuter]

I suspect you get/got some non-winterized fuel at the truck stop and even given your climate the lack of additives and/or blending made the difference. Straight #2 will always give you better power/mileage than "blended" winter fuel up until it is too cold for it to flow, then you realize the error of your ways.

I think you're right. It just popped into my head but I thought it looked different too. The Costco stuff is pure white/clear and this had a slight green hue to it (not algae green, just a tinge). Could just be my imagination too as the volume flowing was much larger than the normal nozzles - less foam too.

 

[turbodieseldyke]

Winterized fuel on coastal so.cal?

 

[jettawreck]

I think you're right. It just popped into my head but I thought it looked different too. The Costco stuff is pure white/clear and this had a slight green hue to it (not algae green, just a tinge). Could just be my imagination too as the volume flowing was much larger than the normal nozzles - less foam too.

All the diesel fuel we get up here is always fluorescent greenish color year around except for the red off-road fuel.
Kerosene is still clear.

 

[jettawreck]

Winterized fuel on coastal so.cal?

No idea where the location he fueled up is/was at.
Most people seldom if ever update their signature lines and such. Mine is certainly out of date.

 

[03TDICommuter]

Southern California, Ventura specifically.

 

[ducatipaso]

i'm cycling through various diesel fuels right now and each has it's own characteristic sound. for example, Propel HPR is quietest at idle, 76 RD is a bit louder and D2 is the loudest.

is it possible your costco is selling renewable diesel?

 

[BobnOH]

................snip...............................Anyways, afterwards I noticed my Beetle was a LOT noisier when cold. Noticeable so until it warmed up. BUT it also felt peppier, and I'm pretty sure I was seeing it haze at night which it's never done. Best mileage on this tank too in a while (48.6 MPG for 721 miles).

Refilled yesterday morning from Costco. Immediately notice the engine is back to being quiet. Too early to tell what the MPG is as I've only put 200 miles miles on it. I'd also feel like it's back to not being peppy. (I have an underpower problem).................snip...............................

Got me curious. Just what was different about the fuel? Believe it or not, sometimes the folks what work at the fuel station know the specifics of what they gots.

 

[03TDICommuter]

Got me curious. Just what was different about the fuel? Believe it or not, sometimes the folks what work at the fuel station know the specifics of what they gots.

This place is unmanned. The building on the property looks condemned. There's not even 'weights and measures' certification stickers on the pumps.

 

[03TDICommuter]

Update on this. After the tank from Silvas Oil Company, I filled up with a tank from Costco. Immediately the diesel noise when cold was quiet again (or at least quiet enough that I didn't think "wow this is clattery"). Costco tank also yielded 48 MPG, but engine didn't feel as peppy.

Next tank, I went back to Silvas as it was $0.50 cheaper per gallon. Clattery engine when cold was back, power was back too - at least more than the Costco tank. Per Burpod's recommendation, I set the timing back to the middle line (was between middle and top). Still noisy when cold, not when warm, though exhaust is more diesel-like. Car is more fun to drive with Silvas diesel. Had to take a different route home this past week, through mountain twisties, and the car did great. Love the Koni reds up front, and the extra power was nice. Beetle swallowed up the twisties nicely. Stop light battle yesterday surprised the heck out of me yesterday too.

So performance wise, diesel from the cheap Silvas station is giving me a better driver's experience.

Any risk that whatever this fuel is doing will harm the longevity of my injection pump?

 

[jettawreck]

I'm guessing the Costco fuel is lower cetane vs the "other" and this "other" fuel is giving you earlier ignition (sort of more injection advance). When I would run advanced timing thru changing the adaptation setting w/VCDS the idle clatter was more pronounced, engine seemed to have more power and/or better fuel mileage (documented).
If you are concerned about less lubricity a few ounces of cheap 2 stroke oil will enhance that. Here in MN we are mandated for 10% +/- bio diesel so I don't worry much about it.

 

[Cosmo's UNA]

FWIW, the Costco in my little town STOPPED SELLING DIESEL AT THEIR PUMPS. It was always the lowest priced, now I have to scramble. Thankfully our great fuel mileage cars give us extra time to shop.

 

[454k30]

I can tell the sound difference between D2, Bio, and the R95 fuels in my engine. The pump noise is much softer with the bio blends, even as low as B20. R95 sounds sharp, like a machine running without proper lubrication. D2 sounds kind of in between the two. I can also tell when I've added power service to the tank. As the engine idles and the now treated fuel is brought into the pump, there is a noticeable change in the sharpness of the pump noise.