Gas Mileage Test

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Important: All information is believed correct, and it is given in good faith, but I cannot be held responsible if it is not correct or does not work for you.

 

There have been many questions raised on the use of premium and non-premium gas in Jaguar cars.  I have both 1995 xj6 4.0 and 1999 xk8 4.0 and I have been using 89 octane non-premium gas on a regular basis in both cars.  I would only use high octane once in a while.  At no time has it given me any performance issues such as pinging, rough idle or stalling.  Both cars performed each and every time I wanted them to.   What I have noticed is that on long trips I would get greater gas mileage with premium.  Local driving in town (stop and go) it did not provide me with the added miles per gallon that would justify the cost of premium.  I am going to post our fuel type, distance and average speed to see how accurate I am and we will see if I am correct in my assumptions.  All information distance, speed & mpg will come directly from the car trip counter and the A/C is on auto.  By the way I have checked this many times by manually calculating the mpg and found that the trip counter to be accurate.

I have been using Exxon middle grade gas.  This comparison will be between Middle and Hi-Test
1999 xk8 101,000 mi 1995 xj6  153,902 mi

Trip  10/17/08 – Highway and town driving sitting in traffic on the beltway, one pit stop 15/20min Me driving

M - Octane 89, Mi 188.2, Av speed 46 mph, MPG 23.9, Duration 3hr 45min

Trip  12/25/08 – Across Catoctin Mt. and over Mt Weather Me driving

M - Octane 89, Mi 76, Av speed 51 mph, MPG 21.4, Duration 45 to 50 min
   
In town traffic Me driving

M - Octane 89, Mi 27.5, Av speed 20mph, MPG 13.5 For the weekend

 		 To and from work Me driving

M - Octane 89, Mi 200, Av speed 40.9 mph, MPG 20.4,Duration 40min each way
   
Trip Back - Highway and in town driving, accident on beltway stop and go, one pit stop 20min Me driving

M - Octane 89 Mi 185.8, Av speed 55 mph, MPG 24.0 Duration 3hr 45min  End Trip

  
   
In town traffic and driving to and from work Wife driving

M - Octane 89, Mi 130.7, Av speed 28 mph, MPG 16.0

 		  
In town traffic and driving to and from work Wife driving

M - Octane 89, Mi 290,  Av speed 35 mph, MPG 18.7

 		  
   
In town traffic and driving to and from work Wife driving

M - Octane 93 , Mi 163.6,  Av speed 30 mph, MPG 17.2

 		  
   

Trip  11/25/08 – Highway and town driving sitting in traffic on the beltway, one pit stop 30min Me driving

M - Octane 93, Mi 188.7, Av speed 54 mph, MPG 24.7, Duration 4hr.

 

  
   
Trip Back - Highway and in town driving, Holiday Traffic stop and go 3mi, one pit stop 15min Me driving

M - Octane 93 Mi 185.9, Av speed 50 mph, MPG 23.6 Duration 4hr  End Trip

 

  
   
Now I ask myself is it worth paying for 93 Octane?  However I did catch fish on Thanksgiving Day!  All over 29in, Had a great time.  
 
   

Trip  7/30/09 – Highway  sitting in traffic on the beltway, one pit stop 15/20min Me driving

M - Octane 89, Mi 188.2, Av speed 40 mph, MPG 20.4, Duration 4hr 25min

  
   

Trip  8/1//09 – Highway  sitting in traffic 2 hrs on the beltway, one pit stop 15/20min Me driving

M - Octane 89, Mi 191, Av speed 41 mph, MPG 22.0, Duration 5hr