Survey for people with and without fuel dilution

[jsphlynch]

Now for configuration. I couldn't really envision a reason why this would matter for fuel dilution, but I figured I might as well include it. Crewcabs outnumbered Supercabs by over three-to-one, and on average had the same severity of fuel dilution.

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[jsphlynch]

A possible clue! The survey asked people to report how many miles are currently on their pickup. The plots of that against the measures of fuel dilution are visually striking: the higher mileage pickups don't have fuel dilution. This trend is particularly striking in the 2019's (blue dots in the figures below), which is notable since these trucks have had plenty of time to be driven all over the place. The other thing that stands out among the low-mileage 2019s is how binary the fuel-dilution severity is. Of the twelve 2019s with 10,000 or fewer miles, six had the fuel smell rated as a 6/10 or higher, five are rated at 1/10, and one is rated as 2/10; none were rated as 3/10, 4/10, or 5/10.

Does low mileage cause fuel dilution? Clearly not, since many low-mileage pickups (including half of the 2019s) don't seem to have an issue. But this data suggests that not driving around much may exacerbate whatever the underlying cause is.

Go drive your trucks more, people!

 

[Texasota]

A possible clue! The survey asked people to report how many miles are currently on their pickup. The plots of that against the measures of fuel dilution are visually striking: the higher mileage pickups don't have fuel dilution. This trend is particularly striking in the 2019's (blue dots in the figures below), which is notable since these trucks have had plenty of time to be driven all over the place. The other thing that stands out among the low-mileage 2019s is how binary the fuel-dilution severity is. Of the twelve 2019s with 10,000 or fewer miles, six had the fuel smell rated as a 6/10 or higher, five are rated at 1/10, and one is rated as 2/10; none were rated as 3/10, 4/10, or 5/10.

Does low mileage cause fuel dilution? Clearly not, since many low-mileage pickups (including half of the 2019s) don't seem to have an issue. But this data suggests that not driving around much may exacerbate whatever the underlying cause is.

Go drive your trucks more, people!

I’m thinking the higher mileage Rangers are higher mileage because they see more extended highway driving as opposed to shorter city trips or short commutes.

On my Ranger short trips, especially in cold weather, is when the oil dilution becomes most noticeable. Longer highway trips appears to boil off the gas in the oil and the level on the dipstick comes back down some.

 

[GitRDone]

Good info, thanks for doing this. Can you post this survey as a sticky? That should gain you a much larger data base over time. Also, does your survey allow for one to edit their responses if their dilution status changes?

 

[jsphlynch]

I’m thinking the higher mileage Rangers are higher mileage because they see more extended highway driving as opposed to shorter city trips or short commutes.

On my Ranger short trips, especially in cold weather, is when the oil dilution becomes most noticeable. Longer highway trips appears to boil off the gas in the oil and the level on the dipstick comes back down some.

A reasonable hypothesis. Let's test it!

For this, I'm going to limit myself to just the twelve 2019 Rangers with 10,000 or fewer miles, and split between low fuel (smell rated as a 1 or a 2) and high fuel (smell rated as 6 or higher).

One of the survey questions asked respondents to estimate how much of their driving was city vs highway vs towing vs offroad. Here's the results:

There is an ever-so-slight trend towards higher proportion of city driving among the high fuel group, but it's so little that I don't think it means anything. The low fuel folks were likely to report towing (3 of 4 people who answered the question), but the only person from the high fuel group who reported towing actually had one of the worst cases of fuel dilution.

So let's look at the other part of your suggestion: short trips. One of the questions asked respondents the length of their daily commute. Check out these results:

Warning: small sample size (especially among the low fuel group, which had several retirees without daily commutes, and so were excluded). The high fuel group had commutes that were, on average, half as long as the low fuel group.

Looking at the raw data, there is a clear break point at 10 miles: Every person in the high fuel group reported a commute of 10 or fewer miles, whereas everyone in the low fuel group reported a commute of 10 or more miles.

 

[jsphlynch]

Good info, thanks for doing this. Can you post this survey as a sticky? That should gain you a much larger data base over time. Also, does your survey allow for one to edit their responses if their dilution status changes?

I think it's up to the mods to make posts sticky.

No, responses are not editable. They are completely anonymous without even an IP logged, so once the submit button is pushed it becomes just a numbered response. If people wanted to update their responses, the combinations of answers are unique enough that they could probably guide me to the right line in the responses.

 

[puckdodger]

done. thanks for doing this, it looks like it was a bit of work

 

[jsphlynch]

I expanded the previous analysis to include all responses, and the conclusion is the same: a commute under 10 miles is associated with worse fuel dilution. Here's the data:

Of the 13 people who reported a commute of less than 10 miles, only one reported no detectable fuel odor and no discernible dipstick rise. That person reported a commute of 9 miles.

At this point, I'm pretty comfortable concluding that commute length is a significant contributing factor for fuel dilution. However, it is not the only factor, as plenty of people with longer commutes are reporting lots of dilution.

Edit to add: 6 new responses have come in since I pulled the data to do this analysis. Of those 6 new responses, only 1 reported a commute of under 10 miles. Anybody want to guess whether or not that person has fuel dilution?

 

[Samsquanch]

I haven’t taken it yet since I am waiting to include my oil analysis date for 2000 and 3000 mile intervals but are warm up times included in the survey? Things like warm up times and idling a generally considered to be contributing factors to fuel dilution.

 

[jsphlynch]

I haven’t taken it yet since I am waiting to include my oil analysis date for 2000 and 3000 mile intervals but are warm up times included in the survey? Things like warm up times and idling a generally considered to be contributing factors to fuel dilution.

I didn't explicitly ask about warmup times, but information about using remote start is included, which I hope will get at the same general concept.

 

[jsphlynch]

Next question: when did people first notice signs of fuel dilution? The answer: usually pretty early in their ownership. 62% of respondents with fuel dilution first noticed it within the first 2000 miles; 86% noticed within the first 5000 miles.

I know there's been a person or two on the forum who reported that the problem suddenly arose after appearing normal for quite some time. These results, however, indicate that those cases are unusual. People are noticing the fuel dilution so early that to me it appears to be a characteristic of their trucks from day 1. If there's an underlying mechanical problem, it's leaving the factory with that problem. On the other hand, this is consistent with low-moderate fuel dilution being a consequence of a person's driving habits and conditions.

 

[Texasota]

This is excellent and fascinating data, Joe. Thanks for all the work you put into this.

 

[jsphlynch]

Next up: Drivetrain. Looks like people really like to have 4-wheel drive, as only 10 respondents listed rear-wheel drive (including Fx2). For the purposes of fuel dilution, it doesn't look like it makes any difference which you get. The average values for both fuel odor and dipstick rise are slightly higher on the rear-wheel drive vehicles, but the difference is well within the standard error.

 

[jsphlynch]

Here's an interesting result: trucks with an FX package (either Fx4 or Fx2) trend towards lower fuel dilution than those that don't. It's not a huge difference, and there's quite a bit of underlying variability (p-value for odor is 0.21, and for oil rise is 0.11), so go ahead and make your own conclusion about whether this means anything. I wouldn't have expected any of the FX improvements to have a significant effect on the fuel, but perhaps people who prefer the FX package are the sort of people that drive their trucks harder and get the oil warmer?

 

[Mike C.]

Here's an interesting result: trucks with an FX package (either Fx4 or Fx2) trend towards lower fuel dilution than those that don't. It's not a huge difference, and there's quite a bit of underlying variability (p-value for odor is 0.21, and for oil rise is 0.11), so go ahead and make your own conclusion about whether this means anything. I wouldn't have expected any of the FX improvements to have a significant effect on the fuel, but perhaps people who prefer the FX package are the sort of people that drive their trucks harder and get the oil warmer?

Awesome data analysis.

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