If the spark plugs in your Subaru Forester SG are worn or incorrect it can lead to poor performance. Additionally, it is also important to make sure that the spark plugs are replaced at or before the recommended service interval.
To help you with all of this, we have put together a short guide on the best spark plugs to use in a second generation Subaru Forester and when to change them.
What are Some Signs of Bad/Worn Spark Plugs?
Before we dive into what spark plugs to use, let’s take a look at some signs that may indicate the spark plugs in your Forester SG need replacing.
Reduced fuel economy – Is your Forester travelling less distance on a tank? If so, it may be down to dirty or fouled spark plugs. A set of new plugs could fix your fuel consumption issue, saving you money at the pump.
Rough starts – Do you notice that your Forester is a bit rough when it starts or does it sometimes not want to start at all? Starting issues can be caused by a whole range of different problems, but the spark plugs are a common culprit. If the spark plugs in your Subaru aren’t up to scratch they won’t create enough spark to get the motor running.
Reduced acceleration – Have you noticed that your Forester SG is not as fast as it used to be? Bad spark plugs are one of the many common causes of performance loss, and as they are easy to replace, changing them should be one of the first things you do.
Rough Idle – Like most of the other problems listed above, this issue can be caused by a whole range of different issues, but bad spark plugs are often a common culprit.
Misfires – Is your Forester SG misfiring at all? Once again, issues with the spark plugs are a common cause of misfires.
What Are the Correct Spark Plugs for a Subaru Forester SG?
The standard spark plugs for a second generation Forester are NGK PFR6B (platinum) plugs, however, many owners with modded cars like to run NGK PFR7B plugs, which are one step colder.
Iridium plugs also come highly recommended with LFR6AIX plugs being the equivalent to PFR6B ones, while LFR7AIX are comparable to PFR7B plugs and are once again more commonly used on modified Forester SGs.
Copper, Platinum or Iridium
While copper spark plugs tend to offer the best performance, many Forester SG owners do not use them. Copper plugs do not last as long and as replacing the spark plugs in a Forester SG can be a bit of a time-consuming process, many owners tend to go with iridium ones. Platinum plugs are cheaper than iridium, but they do offer worse performance.
Other Things to Check
When you are replacing the spark plugs it is a good idea to check the spark plug wires to make sure they are in good condition. You should also take a good look at the old plugs as they can give you a good indication of the health of the engine inside your Forester SG. To find out more about this check out this spark plug analysis guide.
When Should the Spark Plugs Be Changed on a Subaru Forester SG?
Platinum and iridium plugs should be replaced every 96,000 km (60,000 miles) or so. Some owners like to change them more frequently than this, but it is really up to you. If you plan to use copper plugs they will need to be replaced every 16,000 – 32,000 km (10,000 – 20,000) miles, with turbocharged cars chewing through their spark plugs at a faster rate.