318is versus 325i

John Avis by | October 11, 2012 | E30 E36

Having owned four 318is's and now a 325i for a few months I am ready to give my thoughts on the pros and cons of each model.
Having owned four 318is's and now a 325i for a few months I am ready to give my thoughts on the pros and cons of each model.

The main differences between these models is the engine, of course, so my comments will directed this way, rather than comparing things like suspension characteristics. Also I will be talking about 318is's with the M42 engine rather than M44, although the two are very similar so most comments should apply to the M44 as well.

Let's start with fuel economy. Fortunately I have driven both models over the same route day after day so I have an accurate comparison. The 318is wins of course, averaging 8-8.5 l/100km. The 325i is surprisingly not far behind at around 10.0 l/100km, a difference of 1.5 to 2.0 l/100km. What is the difference in fuel cost I hear you ask? If we used 400km a week as an example, then the extra 6 litres per week at A$1.50 per litre will cost an extra $9 which is $468 per year. Incidently, both models require a minimum of 95 octane fuel (premium unleaded).

Now, moving on to the engine characteristics. Compared to the 318is, the 325i engine is so much smoother. It's not that the 318is is harsh, just that when you drive them back-to-back you notice how much smoother the six is. It also makes a beautiful noise, with different noises at low and high speed that will all be appreciated by enthusiasts. The four cylinder is more noise than music. It might just be my 325i, but the six cylinder is the louder of the two models (not a complaint).

On to more important things. Like performance.

Both engines are happiest at higher rev's. I find even the 325i a bit of a slug at lower engine speeds, which came as a bit of surprise. Below somewhere around 3,000 rpm I don't think there is too much difference in performance. Of course the 325i has the edge but the difference doesn't feel that great. Both cars accelerate well above 3,000 rpm (325i) or 4,000 rpm (318is) and are well suited to motorway driving where they have strong acceleration even in top gear around the legal limit. According to road tests I have read the difference is about 2 to 2.5 seconds for zero to 100 km/h.

Maintenance-wise both cars have timing chains, automatic adjustment of valve clearances (hydraulic) and distributor-less ignition so maintenance items are similar and can be as simple as fluids, filters and spark plugs. The only differences being in the favour of the four cylinder model, which are ease of access (there's a lot more room at the front of the engine particularly), and volume of fluids required (the 325i has a much larger oil capacity).

Both engines are known to be very reliable with some exceptions. Mostly the exceptions are the cooling system, and problems are similar on both models: thermostats and water pumps. Again the 325i has a larger coolant capacity. Some 325i models may also have a water pump with a fragile plastic impeller, or a fragile plastic thermostat housing.

It's fairy common knowledge that inline six cylinder engines are more likely to go through head gaskets, although I am not sure if this is a common issue with the M50 engine.

My 325i is an early model. Later models have variable valve timing (VANOS) which is known to be problematic and require maintenance and repair over time. None of the 318is engines have VANOS.

So in summary the 318is is the economical choice, but still offers good performance. If you want to win traffic light grand prixs or you favour engine music over the radio then the 325i is by far the best choice.

Related Posts

E36

1998/1999 BMW 318is Sport (Australia)

by John Avis | March 22, 2017

In 1998, near the end of the E36 life, BMW Australia introduced a limited edition version of the 318is called the "Sport".


E36 Technical Tips

BMW E36 window stuck in open position

by John Avis | December 21, 2016

My passenger side window on my 1998 318is coupe has been stuck in the closed position for some time. I can usually get it going by removing the door trim and then hitting the window motor with a mallet. As it is summer and hot and my air conditioning also stopped working some time ago, I thought I would try and get the window working.


E36 Technical Tips

How to fix BMW E36 squeaking and grinding steering wheel

by John Avis | June 17, 2016

If you hear a squeaking noise coming from behind your 1991 to 1998 BMW 3 series steering wheel, or possibly the steering doesn't feel so smooth and maybe binds every now and then, then there's something you can do fairly easily to try and fix it.

Comments

Victor G.

by Victor G. | April 19, 2014

Hi, this blog is very nice and I have a question, where do you buy the cart Parts

Reply

John

by John | May 19, 2014

If you are buying a few parts at a time it's often cheaper to buy from overseas, either Schmiedmann or Pelican Parts. Otherwise for single parts BMW, one of the BMW specialists or eBay. I recently bought about 10 parts through Schmiedmann for about $230 shipped. The local BMW dealer wanted $550 for the same parts, even at trade prices.

Reply

Leave a Comment
Tags
E30 E36 E46 Magazine Articles My 1990 318is My 1991 325i My 1994 318is My 1995 M3 My 1997 318is My 1998 318is My second 1990 318is Technical Tips

About me

I am a bit of a 3 series fanatic, having owned a couple of E30s and a few E36s, plus a few parts cars. I like the combination of the compact size, good performance and handling, and that they are more sports sedan than an impractical and extrovert sports car. This blog is a place to share my experience and knowledge.

Subscribe

Get the latest posts delivered to your inbox.