E5 or E10 Fuel

[Indalo]

I’m learning a little more each time I drive my Tucson Hybrid.

Today rather confirmed for me that (1) the car is running like a dream and (2) the time spent on battery-only driving has increased, all since my recent re-fuel at Costco, opting for the E5 potion on that occasion. Don’t misunderstand me; I’m not complaining that the car was problematic on its recent E10 diet of less petrol and more ethanol but on today’s odyssey to Cambridge, a frequent event for me, the car was noticeably spending longer periods on battery alone than I remember through the previous tankful of E10.

The mileage to date is nearing the 1100 mile mark so I’m making no claims about the overall economy and will reserve my opinion until I refuel again and do the necessary arithmetic. There is nothing to be learned from any single trip as my credit card only understands how much the fuel cost and I can do the rest using the odometer and/or trip meter readings. All this nonsense about, “.......but I get over 60 on a run!" is just crap! It’s average fuel consumption over the piece that counts; not just the downhill stretches but also the 70mph driving on A-roads and motorways plus the uphill and heavy traffic elements that all contribute to ascertaining the typical average fuel consumption achieved right across the four seasons.

At the end of today’s excursion, I felt quite uplifted by the way the car performed so, psychologically, the car seems to respond better to E5 than to E10 but it’s early days yet so I’ll wait to see how the numbers pan out over the piece. Experience informs me that I can expect to see some improvement in mpg once a few thousand miles are on the clock and that will occur over the winter months but I expect to see some good mpg allied to decent performance by the time we get to midsummer 2024.......at least, I hope so!

[Mar10]

I haven't personally noticed any difference in either performance or economy between E5 or E10, I do sometimes run through a tank of E5 though as I know it can do some good for the engine. I think it would be hard to make any meaningful comparison in terms of economy as other variables seem to make a much bigger impact than the marginal gains of a different fuel. The weather, traffic, time spent at speed, hills and rate of acceleration all seem to make a more noticeable difference on the MPG achievable with the hybrid.

I make the same trip to the gym on a morning, it's about a 10 min drive and mix of suburban 30 roads and a stretch of 60 A road. I don't go over the speed limit but the MPG that I achieve ranges between 25 to 48 depending on weather, how much I'm in a rush and traffic. With variation like that I don't think I'd notice the benefit of a penny here and there because if fuel!!

[Saltcreek]

There seems to be a little misconception on what the difference is and what the benefit is, if any for the Tucson. I would not be concerning myself with the ethanol content, that is not important however the octane is. The higher the octane value of a fuel the more resistant to combustion which means you are going to be able to make more power via tuning (timing/leaning out) before experiencing pinging/knock. On the stock ECU/maps you will not ever see a noticeable difference in power between the 2 fuels as the ECU is simply not tuned for it. While there is room for the ECU to adjust timing/fuel depending on what conditions you are driving in, it will be limited on how far it can go. Also, since octane is a combustion inhibitor it will have no effect on your range - there are too many variables for anyone to ever accurately tell the difference and you would not ever recognise a cost savings.

With that said, does it mean that running E5 is pointless? Not necessarily, it depends on how you drive, where you drive, and what conditions. If you drive like a normal human being in the UK and only pin it from time to time then I cannot see any benefit to running E5. If you are planning a trip to the mountains/hills, hot weather, hard driving then there can be a benefit to running E5 as the harder you work the engine in warmer weather/higher altitudes then the higher cylinder temperatures you will experience which can lead to knock. Keep in mind that if you are switching to a higher octane fuel then the ECU will need time to adjust (I used to be able to soft reset my Subaru to speed this process up, but I doubt this is possible with the Tucson). I would guess you would need a good 30-40 miles for it to adjust.

I run E5 right now because the engine is new and I am still learning how the car responds. Ill be going to E10 in a couple of tanks however I have no rational reason to be running E5 when it comes down to it.

[PhilHornby]

This is the most recent Petrol comparison test I can find.

On the downside, it pre-dates the 'ethanol' question, but it does show differences between different fuels. There is no fuel economy comparison - it focuses purely on power and spoiler alert, that difference is only around 2%.

The question is: Is the extra power a result of different fuels containing different amounts of energy (which would translate to more mpg, if you don't actually use that power), or is it the engine management responding to octane rating differences - which wouldn't.

I had a look at both the Shell and Esso web sites, to see what they claim the difference is in their current ' Performance Fuel', but found no useful information.

[Saltcreek]

This is the most recent Petrol comparison test I can find.

On the downside, it pre-dates the 'ethanol' question, but it does show differences between different fuels. There is no fuel economy comparison - it focuses purely on power and spoiler alert, that difference is only around 2%.

The question is: Is the extra power a result of different fuels containing different amounts of energy (which would translate to more mpg, if you don't actually use that power), or is it the engine management responding to octane rating differences - which wouldn't.

I had a look at both the Shell and Esso web sites, to see what they claim the difference is in their current ' Performance Fuel', but found no useful information.

The extra power is from the octane differences and a little bit from supplier additives. 4bhp is a value that you would not even feel and on any given day your car will either be delivering slightly more or slightly less than the 227bhp depending on the conditions.

Without going into much detail the higher the octane value will allow you to advance the timing further and lean out the mixture further while generating more power. The risk is if the fuel pre detonates then you can get engine damage over a long term or when you are pushing the limits. Using less fuel to make power is where the efficiency gain is, not that there is more energy in the fuel itself.

While the higher ethanol content fuels do have less energy in them it would be very hard for you to measure any range gains and even if you could i would be very confident in that you would not be saving money over the cheaper fuel.

Back in the day in Canada when I was part of a very large Subaru club we used to data log all the different suppliers fuels and make recommendations on which vendors had better quality fuels. Even back in 2005 there was 1 vendor in Canada that supplied ethanol fuel which also had the highest octane value. This was our preferred fuel for our modified and tuned cars. On the flip side, PetroCanada, consistently caused our cars to ping, pull timing, etc so we avoided this vendor like the plague.

[PhilHornby]

The extra power is from the octane differences and a little bit from supplier additives.

However that hypothesis is disputed by many, many sources. I always find Quora.com users to be an engaging lot on subjects like this...

But it's probably a moot point - the question is: Is there a benefit to filling up with the more expensive fuel?

I don't think we Tucson owners are particularly interested in more power - but better fuel economy could make it worthwhile.

A month ago, I did a 600 mile day-trip in six stages (i.e. coffee breaks etc). This was at motorway speeds and I noted that the economy for each leg of the journey started with a "3" - let's say the average was 38mpg. Locally to me, Texaco Super Unleaded/E5 is 165.9p/litre and Regular Unleaded/E10 is 147.9p/litre. That is a ratio of 1.122:1, so the car would have needed to do approx. 43mpg to break even. (I'm due to repeat this trip in September, so I may experiment then).


As a complete aside, I was searching through the PDF version of the Tucson manual (the USA/Canada version, since I don't have such a thing for the UK) and I came across the following strange section, regarding how often you should add Hyundai Fuel Additive, if you can't fill up with 'approved' fuel (see www.toptiergas.com)

A cut-down version of this appears on Page 9 of the UK manual, but of course, we don't have 'TopTier Fuel', so it's a lot vaguer as to what constitutes 'good quality petrol'

A snippet:-

[Saltcreek]

The extra power is from the octane differences and a little bit from supplier additives.

However that hypothesis is disputed by many, many sources. I always find Quora.com users to be an engaging lot on subjects like this...

But it's probably a moot point - the question is: Is there a benefit to filling up with the more expensive fuel?

I don't think we Tucson owners are particularly interested in more power - but better fuel economy could make it worthwhile.

A month ago, I did a 600 mile day-trip in six stages (i.e. coffee breaks etc). This was at motorway speeds and I noted that the economy for each leg of the journey started with a "3" - let's say the average was 38mpg. Locally to me, Texaco Super Unleaded/E5 is 165.9p/litre and Regular Unleaded/E10 is 147.9p/litre. That is a ratio of 1.122:1, so the car would have needed to do approx. 43mpg to break even. (I'm due to repeat this trip in September, so I may experiment then).


As a complete aside, I was searching through the PDF version of the Tucson manual (the USA/Canada version, since I don't have such a thing for the UK) and I came across the following strange section, regarding how often you should add Hyundai Fuel Additive, if you can't fill up with 'approved' fuel (see www.toptiergas.com)

A cut-down version of this appears on Page 9 of the UK manual, but of course, we don't have 'TopTier Fuel', so it's a lot vaguer as to what constitutes 'good quality petrol'

A snippet:-
Toptier.jpg

Ummm, that Quora link agrees with me, not disagree. Octane is the reason you can make more power, it has nothing to do with the energy content of the fuel. Higher octane means you can tune more aggressively and therefore make more power. Keep in mind that the more power you make with any engine the hotter the combustion chamber will be, thus the need for higher octane to make the fuel more resistant to pre detonation. I am keeping this simple because engine tuning isn’t something that can be covered over a few posts.

Also, in that link you posted it clearly stated that higher octane fuels will not give you any extra range because the octane is only required when you are pushing/working the engine. When you are doing normal everyday driving the factory maps are not going to change much, if any, between the 2 fuels.

[PhilHornby]

...I am keeping this simple because engine tuning isn’t something that can be covered over a few posts...

I can fill in the gaps ... it's a subject I've been studying since 1977 It's a pity I don't have the skills to actually build the Flat-6, 50cc two-stroke I designed

Also, in that link you posted it clearly stated that higher octane fuels will not give you any extra range because the octane is only required when you are pushing/working the engine. When you are doing normal everyday driving the factory maps are not going to change much, if any, between the 2 fuels.

But that is the basis of the "more energy" theory. My bike is normally aspirated, does not have a knock sensor and always runs "Open-loop" (no lambda sensor) - yet it does achieve more mpg on "Super Unleaded". The Mazda KL03 engine that was in my old Ford Probe was also normally aspirated and definitely achieved more mpg (on Shell Optimax, back then).

As I said though, it's all a bit moot, until someone quantifies the fuel economy gain on the Tucson.

[roadster]

The owners manual does suggest a preference for E5 so that's what I use. This is coloured by a rash of problems I have had with various other engines in lawn mowers and other petrol powered garden equipment as well as a Chinese built motorcycles. There is no doubt that Hyundai and other manufacturers have put in precautionary changes in new vehicles and this includes automatic ignition timing and fuelling adjustments that detect both detonation and exhaust oxygen and temperature sensors. Long term effects on rubber and plastic components in the fuel system are more difficult to be certain about.

[italianjob1970]

The owners manual does suggest a preference for E5 so that's what I use. This is coloured by a rash of problems I have had with various other engines in lawn mowers and other petrol powered garden equipment as well as a Chinese built motorcycles. There is no doubt that Hyundai and other manufacturers have put in precautionary changes in new vehicles and this includes automatic ignition timing and fuelling adjustments that detect both detonation and exhaust oxygen and temperature sensors. Long term effects on rubber and plastic components in the fuel system are more difficult to be certain about.

My manual suggest anything up to E15 is fine, so no worries.