Fuel and Italian Tune Up!

[defever]

Hello B5 drivers,

Been quiet here for a while so I thought I'd instigate something on my recent experiment...

Earlier this year, I experienced "limp mode". I successfully cleaned up lots of places and I no longer have limp mode. That really got me into "how do you keep an old diesel at its best performance?". So I've been looking at all sorts of things from EGR blanking, turbo upgrade, decat, fuel injectors, remapping, etc. Some are fairly easy "mods" and some need time, skill, and CASH. I don't have much money...

I came across the old debate of "where you fill up matters". Apparently, diesel itself seems to be exactly the same regardless of where you fill up. But what matters is the "additives" mixed into the fuel AFTER the fuel is distributed at a refinery (and supplied at a pump by different brands). I've been buying my fuel at Sainsbury's (rumour is that BP supplies Sainsbury's fuel) for years up until recently. I've been testing out BP Ultimate for the last four or five tankfuls at a price of £5-6.00 more compared to Sainsbury's (hey, you still get 1 Nectar point per liter).

Another thing I've been testing out is the "Italian Tune Up" (ITU). There seems to be variations on exactly how you conduct the tune up but essentially you drive at high rev to heat up the engine and "burn off" the carbon deposits in the system. I've been doing this on a motorway for 8-10miles on 3rd gear at 70mph (just below the red line) well after the engine is heated up to 90C. Then followed by 5th gear at 60-65mph (up to 2500rpm) for the rest of the journey. I've been doing this since I started going to BP for its Ultimate Diesel fuel.

Well before the limp mode, my combined mpg was nearer to 56mpg, DIS measure was around 6.9mpg off. Since I swapped to BP Ultimate and doing ITU every week, it's been around 55mpg, and DIS measure dropped to being off by around 5.5mpg.

It's hard to conclude whether the fuel and ITU is helping the performance / mpg / etc. But what I can say is that I never used to go above 2000rpm before limp mode, EVER. Now with a different fuel and regular ITU (and frequent hard acceleration), I'm only off by 1mpg. I work the engine A LOT more now and it's still just off by 1mpg than pre-limp mode state. The engine now feels much "smoother" and more responsive, but I'm aware that this could be placebo (the fact that I never went above 2000rpm before).

I think I'll carry on with BP Ultimate and regular ITU to maintain my engine.

What are your thoughts on being specific about your fuel and doing an Italian Tune Up??

[zollaf]

deffo, i can get 50 odd miles extra to a tank if i use tesco diesel, which contrary to pop belief is good stuff. can't really say about the itu as my poor 80 is slaughtered evertime we drive her but this has never broken her, and she uses no oil. i do find however that planting ones foot to get upto speed as quick as you can , then cruising at that speed is more efficient than gradually accelerating, as accelerating uses more fuel and the less you do it, the less you use.

[defever]

Yup I agree,

there definitely seems to be a trial and error approach to finding the right fuel for each car. BP Ultimate generally gets a good punt and Shell's equivalent premium diesel seems to produce very mixed opinion. Some swear by supermarket fuels, some even claim that it written off certain engines. I think it's trial and error but BP Ultimate claims that its fuel cleans the injector nozzles and everything from the chamber and beyond; I'm going to use the Ultimate for another tankful and might rever to BP's normal diesel (pretty much same price as Sainsbury's diesel) and see how it goes.

I've read and seen a YouTube clip by a guy in Scandinavia (I think) who put really good advice on hyper-milage techniques. Fast and quick acceleration, to the contrary to general public's understanding, is in fact more fuel efficient than snailing up to the speed.

More experiment to do but I thought I'd share what I learned so far!

Happy motoring everyone.

[defever]

Little update on this, I did further observation (not scientific!).

I tried a tankful of both normal BP diesel and Shell V Power since my last post and this is what I got:

Normal BP diesel (108.9p/L): 52mpg (DIS discrepancy 6.5mpg)
BP Ultimate (118.9p/L): 55mpg (DIS discrepancy 5.5mpg)
Shell V Power (118.9p/L): 56mpg (DIS discrepancy 4.1mpg)



Simple calculation demonstrate that the premium diesel costs 10p/L more than the normal fuel. So if you fill up 50L, then that's £5.00 more for premium fuel. But premium fuels gave higher MPG, which reduces running cost. But by how much?

So I did a geeky calculation given a journey of 700miles for each fuel. To cover 700miles, it requires:

61.20L of Normal BP diesel (108.9p/L, 52mpg): PRICE £66.64
57.86L of BP Ultimate (118.9p/L, 55mpg): PRICE £68.79 (+£2.15 than normal diesel)
56.83L of Shell V Power (118.9p/L, 56mpg: PRICE £67.57 (+£0.92 than normal diesel)

So, in essence, I only pay £2.15 more for better fuel efficiency for BP ultimate and £0.92 more for V Power!
That extra £5.00 at tankful of premium fuel doesn't sound too bad now (as long as my calculation was correct).

Obviously, there's lots of variables to consider like driving behaviour, weather, wear & tear, town/motorway, etc. and this is a simple observation done on my car so it's not an universal result.

I now filled up with Tesco Diesel to have a go (£103.9p/L)! Zollaf I'll let you know if my car likes Tesco diesel.

[defever]

New year update!

So I tried two tank full of Tesco diesel (103.9p/L and 99.9p/L) for the last month and the average MPG was 52.28mpg (DIS discrepancy 5.9MPG)

So that's not much different from BP normal diesel.
So, you could be right Zollaf, Tesco diesel might be as good as BP normal diesel on my car!

Based on my observations, I think I will stick with BP Ultimate, because there's one station locally (Shell station is no where near me...).

It's been an interesting and geeky observation for the last few months!

[MarkTM]

I always fill up with whichever supermarket diesel is cheaper, so at last Sainsburys fill up of 80l worked out at 91.9ppl (using 8ppl voucher) less £5 of nectar points meant 85.7ppl

But I always add Miller diesel additive and have never achieved less than 720 miles from my 80l tank, which is 40mpg from a 3.0V6

I did find that fitting slightly larger tyres meant that a) my speedo reads accurately and b) my DIS was 1% rather than 6% out, so in summer run 245/45/18 as opposed to OEM 245/40/18.

[Col]

Pulse and Glide...

Is what it is all about if you want silly good MPG's. By default you are always doing ITU's as well. Win-win.

[defever]

I did find that fitting slightly larger tyres meant that a) my speedo reads accurately and b) my DIS was 1% rather than 6% out, so in summer run 245/45/18 as opposed to OEM 245/40/18.

Thanks MarkTM, that's an interesting point; I often wondered the relationship between tyre size, speed and MPG. Perhaps I'll look into this in near future.

Pulse and Glide...

Is what it is all about if you want silly good MPG's. By default you are always doing ITU's as well. Win-win.

Col, I think that's also a very good advice. I pulse and glide all the time, especially on motorways. But I pulse more frequently and in small amplitude than you might. If you associate pulse and glide with ITU, then I assume you accelerate quite hard, cruise until the speed drops considerably and then pulse aggressively again to get up to the speed? I'm pulse very gently within 2-3mph of the speed I want to maintain. And then do 10miles of 3rd gear belting in the middle of the journey.

How do you pulse and glide?

[Gazwould]

Just add 2 Stroke .

[MarkTM]

Just add 2 Stroke .

yep I do too...mix it with the Millers. Didn't mention as a bit controversial as is scientifically proven to cause build ups on injectors.