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Item: 970582

Bosch 521 Super 4 Spark Plug x4


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  • Bosch 521 Super 4 Spark Plug

    Featuring a unique state of the art design, the Bosch 521 Super 4 Spark Plug results in improved engine smoothness and acceleration.

    Bosch 521 Super 4 Spark Plug Extra Info

    • Superior engine versatility
    • Electrode gap adjusted ex factory
    • Noticeable improvement in acceleration
    • Significantly improved engine smoothness

    Additional Information

    Please check with your vehicle manufacturer or workshop manual to confirm the suitability of this part for your vehicle.
  • Hex Size: 16
    Thread Length mm: 25
    Thread Size mm: 14 x 1.25
  • Rated 4 out of 5 by 6 reviewers.
    Rated 5 out of 5 by Smooth Power Boost Brought these for my 1.7 1998 Ford Puma (on trade) and they seem to have made a difference. Its a sporty engine and the throttle response is crisper and starting seems smoother. I am yet to see if fuel economy is better (lots of motorway miles) but the logic of 4 electrodes for grounding and allowing the spark to find its best way to earth for the operating conditions seems fair. These should last longer as any arcing wont be on just one ground electrode. Its advisable to squirt the threads with WD40 or copper grease to ease removal next time they are taken out. Also ensure the threads on the head are clean and do them finger tight first! 03 May 2013
    Rated 1 out of 5 by Loss of torque, avoid! I've got a 1,6 2007 Focus at 53k and these plugs have caused a loss of torque over my 15k miles old plugs the engine seems to run fine but it's lost that urge to pull at lower revs for overtaking at classic 50-70. Why do you need 4 contacts anyway? first time it picks one the other 3 dirty up and will never work again, just get in the way of clean combustion. Fuel milesage has also dropped by about 3mpg will be replacing with NGK Platinum if i can find the receipt for these. 18 February 2013
    Rated 5 out of 5 by Great product, would recommend Car was running a little off and was due a service, so decided to pay the extra couple of pounds and try out these plugs. So glad I did, they have made and noticeable difference instantly. I live in a hilly part of West Yorkshire and there is far greater power when going up hill now, with less need to change down the gears. All in all the car feels smoother, with more power throughout the whole range. I would definitely recommend these plugs 02 September 2012
    Rated 5 out of 5 by A good product I can feel the difference while driving. I am getting more power. 05 April 2012
    Rated 3 out of 5 by Average Thougth i'd give these a try as the old motorcraft ones were getting tired and to my surprise there was no difference in performance apart from the misfire disappearing and economy the same so don't pay out thinking these will make your car go faster as they are no better than the cheaper ones. 18 February 2012
    Rated 5 out of 5 by Bosch Super 4's Brought a set for a 02 1.6 Focus didn't solve the issue I had with the car but what a diffrence they have made acceleration is so much smoother would recommend to anyone. 06 February 2012
    • 2016-09-29 T08:21:55.276-05:00
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Some of the parts we sell here at Halfords have been reconditioned. These will carry a Refundable Deposit or an extra surcharge amount. When you add one of these reconditioned items to your basket, we'll add this extra cost automatically.

Once you've sent us your old item we'll check it over, and then refund you the full surcharge as long as everything is ok.

Before you return your old unit please make sure it's in re-serviceable condition. So if you're returning caliper casings, you'll need to double check they aren't badly damaged or broken. If the part you've sent is found to be unserviceable, we reserve the right not to refund the surcharge.

Please note that if you're returning your old unit to our National Returns Centre then this will be at your own expense.

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Bosch Spark Plugs

Bosch 521 Super 4 Spark Plug x4

£21.49 The Bosch 521 Super 4 Spark Plug helps improve your acceleration and engine smoothness.