Well, it took a few months, but it looks like the winter blend of gas has finally caught up with me. My '07 VDP has begun the rough warm start up issues again just like last winter. It only occurs if the car has been driven and then turned off for around 5 to 20 minutes. Then when I go to start it, the engine hesitates and sometimes dies. Other times it will start and run rough for 5 to 10 seconds and then smooth out. So far it has only happened twice this year.

Last year I even got the check engine light a couple of times for cylinder misfires. It was on different cylinders at different times. Not limited to certain ones. This year I have not had the check engine light yet.

Last year I ran two cans of BG44 though her and the problem went away. This year I am going to try something new. I used to have a Mercedes E320 that had a similar problem. I switched to mid grade gas and the issue went away. This was suggested to me by the MB tech at the dealership. I ended up making the fuel switch permanently and using mid grade year round with no issues. I ran that car like that for about nine years and put 150K miles on it with mid grade fuel with no additional problems.

Before I put another two cans of BG44 in this year I am making the fuel switch and will see if that helps any. Just put the first tank of mid grade in yesterday. I will keep the forum updated on the results.

 

I have been running the mid-grade gas for two weeks now and have had no warm start up hiccups. I am hopeful I may have found a solution to the problem and may even save money by using mid-grade rather than premium.

 

I had several "Check Engine" episodes last year, all stopped when I started using Shell Premium!
All gasoline may be the same from the refinery but, have different additives at the pump. Somehow it makes a difference in my VDP!

 

When the price of gas went up I tested all my cars on lower grades. Found mid grade runs just fine in all of them, so that's what I have been using since '08. The low grade rattles them all, and the premium is just spending money for no difference in performance.

I have had several bad tanks of fuel over the years, so now I only use fuel from decent stations...no 7/11's anymore! If a station's pumps are ragged out so you can't get a receipt and the buttons are inop...chances are they will not purchase the best gas either. Nothing is more frustrating than spending time diagnosing engine problems that turn out to be bad gas.

An occasional fuel treatment removes any water condensation that has accumulated in the tank.

John

 

Just had my xj super 8 in for a engine light, the mechanic said they had to reset the computer, i have 30,000 miles on this car and it has been in the shop two times for hard starts. I use premium gas without etheynol. Any suggestions?
Thank You

 

Fancfre, do you have the hard starts all year or just in the winter? My issue has only been in the winter and seems to be attributed to the winter blend of fuel. I was always using BP Ultimate gas and still had the issue.

Last year, running two cans of BG44 through the system seemed to work, (One can in a full tank, one normal tank of gas, then the second can in the third tank) but i did it late in the winter season and am not sure how long it would have lasted if I had done it this early. This year I have switched to mid grade gas and the issue has gone away. The rough start began in early December and after about two weeks of it I switched to the mid grade and have had no rough start issues since.

However, recently I have noticed my mpg drop. I am not sure if it is the switch to mid grade, the colder weather in general, or if I may have a thermostat going bad. I am still watching everything to see.

For my two cents, I would try switching to a mid grade gas as it not only doesn't cost you anything, but it will actually save you money at the pump. If that does not work then run the BG44 through her.

Good luck and let us know what you do and if it works.

 

It's possible that the drop in efficiency between mid grade and premium could be from the knock sensors dialing back the timing, making the engine run retarded. This will affect mileage badly. The bad thing about dropping fuel grades is that you don't know how much effect it is having on the car as it adjusts itself, it will decrease performance and efficiency quietly.

 

You have a point there, I tried mid-grade last year and my VDP listed all sorts of Fuel-related codes. it then settled down for a few days then started rough for about a week. I switched back to premium and have never had any more problems. I use premium at every fill-up with no starting problems.

 

Oldmots, you may be right. I switched back to Premium on my last fill up to see if the mpg goes back up. If so, and I start getting rough starts again, I will put some BG44 thru the tank and then keep my fingers crossed.

I guess I could always move South so I don't have the issue in the Winter.

 

Here is an excerpt from the Owners manual:

 

A little more info on this, the 4.2 NA engine used in the XJ8 has 11-1 compression, bad things happen with low fuel grades in engines like this. The best premium is just barely good enough to handle an engine designed like this one. It doesn't make sense to have a car like this and use cheap fuel in it, it is false economy.

 

I gave up on the mid grade. My mpg is back up where it normally is now that I have gone back to premium. Now I will just wait to see if the warm start-up issues rear their ugly head. If so it will be time for some BG44.