Good, bad or ugly? Bosch Spark plugs re: 1994 850 B5254F

[cn90]

Just replaced my Bosch spark plugs.

4y/25K ago: I used Bosch 7555 (FR7DC), made in Brasil, after 25K miles, the gap went from 0.028" ---> 0.032", which is normal wear/tear.

This time, I use Bosch 79555 (FR7DC+), made in Germany, $1.99/each at Autozone.
I followed Ozark Lee's advice and set the gap to 0.028".

For N/A (non-turbo) engines, I guess you can use either Bosch 7555 or 7955.


See the picture.

Volvospplugs.JPG (150.24 KiB) Viewed 3096 times

[MilehighV70XC]

Is the threaded section on the 7955 plugs longer then the 7555? Maybe it is just the angle of the picture, but the 7555 looks to be shorter.

[SpeedyPete]

Hi Guys: I have been running the Bosch 7955 supper plus in my T5 for years with great success, never a problem. However, I also change them out at 15,000 mile intervals. At $10.00 a set, just part of the routine at 15,000 mile service I do. Best Regards, SpeedyPete

[cn90]

Is the threaded section on the 7955 plugs longer then the 7555? Maybe it is just the angle of the picture, but the 7555 looks to be shorter.

The old plug had some antiseize on it, but if you look carefully, both 7555 and 7955 hae the same number of threads (about 12).

[tjts1]

I've had Bosch 7401 in the 850 since april 2011 and may 2011 in the 960 without any problems. Its a 4 electrode copper core plug (not to be confused with the platinum garbage). This is the first time I've been happy with Bosch plugs in years. Normally I stick with Denso. A friend in the UK turned me on to these and I jumped on them when Amazon had then on sale $1 each.

[jblackburn]

I've had Bosch 7401 in the 850 since april 2011 and may 2011 in the 960 without any problems. Its a 4 electrode copper core plug (not to be confused with the platinum garbage). This is the first time I've been happy with Bosch plugs in years. Normally I stick with Denso. A friend in the UK turned me on to these and I jumped on them when Amazon had then on sale $1 each.

I didn't even know they made such a thing! Any gains that you can tell vs a standard one prong copper plug?

[tjts1]

I've had Bosch 7401 in the 850 since april 2011 and may 2011 in the 960 without any problems. Its a 4 electrode copper core plug (not to be confused with the platinum garbage). This is the first time I've been happy with Bosch plugs in years. Normally I stick with Denso. A friend in the UK turned me on to these and I jumped on them when Amazon had then on sale $1 each.

I didn't even know they made such a thing! Any gains that you can tell vs a standard one prong copper plug?

If there are I couldn't tell the difference from the old copper Denso plugs. At least theres no down side thus far. I'm assuming the multiple ground electrodes will last longer than a single electrode plug.

[waynej]

I am using the genuine Volvo plugs with the 4 ground electrodes.
On the older engines, when we only had 1 electrode we would index the plugs for maximum performance. Champion sold indexing washers of different thicknesses so we could have the gap facing into the direction of airflow in the cylinder.
I am guessing the reason they now have multiple gaps is because in modern engines the airflow changes direction with RPM, especially with VVIS.
The OEM's are expensive. Has anyone compared the performance or mileage between the single and quad gap plugs?

[cn90]

According to the BM E39 forum, similar discussion happens many times and the consensus is:
- Single-prong is better than Quad.
- Indexing spark plug is a myth.

[tjts1]

According to the BM E39 forum, similar discussion happens many times and the consensus is:
- Single-prong is better than Quad.
- Indexing spark plug is a myth.

Well thank goodness we don't drive E39s