Lucas Fuel Treatment and lower mpg?

[Alex110]

I recently purchased an Infiniti I35 with 100K miles. The fuel efficiency was around 22 mpg (measured by myself, trip computer gave me 24 mpg) but I thought it could do better. So I added the Lucas fuel treatment the next time I filled up the car. I added around 5 ounces before adding the 15 gallons of fuel. I have noticed a much lower mpg than I was getting before, really low: the trip computer was giving like 10 mpg at first but now it is up to 18 mpg, visually I can see that the fuel tank is 1/4 empty after driving 50miles ~14 mpg.

I have read places that this treatment could do harm (to some vehicles) to the injectors, fuel line and fuel filter. Is that true and if so what should I do at this point? Maybe there was a lot of dirt in the fuel system and now it is trying to get rid of it thus resulting in lower mpg, could that be so? I am hoping that the problem gradually goes away as I drive the car, I will make the tank full when it gets to the half-mark to lower the concentration of Lucas.

[maxhopper]

I would run that tank out, then fill up again. There's not really too much you can do at this point. In the future use BG 44k fuel treatment - it's great stuff and I've never heard of anyone having any issues with it.

[loystock]

Better use BG44k (per max recommendation, @ $18) or Red Line SI-1 (@ $8) Fuel Injector System Cleaner. Techron is Ok but is not highly concentrated. I'd stay away from any other fuel additive.

[MinisterofDOOM]

Lucas shouldn't do any harm. It consists almost entirely of paraffin. I wouldn't worry about permanent damage, but running one of the above treatments should do more actual cleaning, as they contain more complex and genuinely useful ingredients.

[Alex110]

Well. I just refueled once the tank was half full. After refueling I calculated the mpg and it came out to 15. Now with lucas' concentration less than half of what it was, the car is performing much better, the trip computer gave me a reading of over 27 mpg while driving on the highway (I know it overestimates the actual by about 15%). I just ordered BG 44K and will be using that before I do my next oil change. Thanks for the info guys.

[Alex110]

Well. This is what has happened now. The fuel efficiency is now down to 22 from 27 after I refueled the car. I haven't added any additives. I wonder what is going on, are the injectors dirty, have I damaged the O2 sensor. Anyways, I just got the BG44K today. I am wondering if I should add it at this point in time or wait until my gas tank empties.

Another weird thing is that my car's rpm when I purchased it a month ago was good. I remember that it was less than 3000 when driving at like 70 mph. But then suddenly (don't remember when) it jumped up and I thought my memory was going bad (I am getting older). It went up to like 3300 when driving at 60-65. But last night I noticed that the car is running smooth in the freeway like 2500 rpm when driving at 65. I don't what's going on. Any thoughts?

[DrAg0oN]

Maybe your transmission is starting to slip?? Because that is whats happening with my car..

[Alex110]

I tried BGK44 and well it doesn't seem to have changed my fuel efficiency though it might have done some cleaning. My car never recovered back to its initial mpg of 22, it is now at 20. I wonder if I need to change the fuel filter. As far as my transmission goes it is not slipping, I was a dumbass driving on the 3rd gear instead of drive on the freeway.

[maxhopper]

The fuel filter is built into the fuel pump in the tank, and is supposed to be "maintenance free."

A difference of 2mpg is not much of a difference and can be attributed to any number of variables that take place in daily driving.

[bpomps]

The fuel filter is built into the fuel pump in the tank, and is supposed to be "maintenance free."

A difference of 2mpg is not much of a difference and can be attributed to any number of variables that take place in daily driving.

there is (or was) a thread on here where someone changed the fuel filter and i decided to do mine - and im glad i did.

my fuel filter was oily and very dark and just looked bad. there were also METAL fragments in the housing and stuck to the filter.

i think i got the fuel filter for 15 bucks - at a dealership.

its not really a hard job, you just need to take out the back seat and to get to the tank / housing. make sure you do it with a near empty tank

if you have 100K miles on your max or close to it and you are able to do that job then you should ! im not sure i have pics saved ill have to dig around but i did take some before and after.

[bpomps]

there is (or was) a thread on here where someone changed the fuel filter and i decided to do mine - and im glad i did.

my fuel filter was oily and very dark and just looked bad. there were also METAL fragments in the housing and stuck to the filter.

i think i got the fuel filter for 15 bucks - at a dealership.

its not really a hard job, you just need to take out the back seat and to get to the tank / housing. make sure you do it with a near empty tank

if you have 100K miles on your max or close to it and you are able to do that job then you should ! im not sure i have pics saved ill have to dig around but i did take some before and after.

Here is the how-to,

http://www.shiftice.com/fuel_filter.html

[Alex110]

Thanks bpomps. Very informative. I have to find out if my infiniti's fuel pump location is same as the maxima you posted.