Took a 2 year old BMW 318i Compact for a test drive from Croydon BMW - lovely car only 16,600 miles auto.leather.sunroof etc. but on start up it rattled like a diesl for 2 mins and the oil warning light came on. Checked the oil level under pretence of looking at the engine and it was well below minimum and not very clean. Took HJ's advise and stayed well clear as this engines complex engine valve gear/cam chains could have been be damaged.

The Lesson to pass on to all motorists is that oil will only be good for 15,000 if there is enough of it left in the engine - ie you still have to check the oil evry 2-3000 miles as modern engines do use oil, in fact are designed to I believe.

Another probelm with 15,000 mile service intervals is that Disc brakes can needed servicing much earlier e.g if rears are sticking like on many cars or pads are worn

Charles Fox
South Croydon Read more

Just might be of interest to some of the readers here.

Viscosity Index Improvers.

An oils viscosity will decrease as the engine temperature rises. Viscosity Index Improvers are added to reduce this thinning. They are a key addative in the production of multigrade oils.

VI Improvers are heat sensitive long chain, high molecular weight polymers that minimise the viscosity loss of the oil at high temperatures. They work like springs, coiled at low temperatures and uncoiling at high temperatures. This makes the molecules larger (at high temps) which increases internal resistance within the thinning oil. They in effect "fight back" against the viscosity loss in the oil.

"Shearing"

The long chain molecules in VI Improvers are prone to "shearing" with use which reduces their ability to prevent the oil from losing viscosity. This "shearing" occurs when shear stress ruptures the long chain molecules and converts them to shorter, lower weight molecules. The shorter, lower weight molecules offer less resistance to flow and their ability to maintain viscosity is reduced.

This shearing not only reduces the viscosity of the oil but can cause piston ring sticking (due to deposits), increased oil consumption and increased engine wear.

Like basestock quality, VI Improvers also vary in quality. As with many items the more you pay, the better the finished article and more expensive, usually synthetic oils are likely to incorporate better VI improvers. All other things being equal the less VI improver an oil contains, the better it will stay in grade by resisting viscosity loss.

Which oils require more VI Improvers?

There are two scenarios where large amounts of these polymers are required as a rule.

Firstly in "wide viscosity span" multigrades. By this I mean that the difference between the lower "W" number and the higher number is large for example 5w-50 (diff 45) and 10w-60 (diff 50) are what is termed as "wide viscosity span" oils.

Narrow viscosity oils like 0w-30 (diff 30) or 5w-40 (diff 35) require far less VI Improvers and therefore are less prone to "shearing".

Secondly, mineral and hydrocracked (petroleum synthetic oils) require more VI Improvers than proper PAO/Ester (Group IV or V) synthetic oils as they have a higher inherent VI to begin with, this is due to differences in the molecular structure of the synthetic base oils compared to mineral oils.

It is a fact that many synthetics require significantly less VI Improver to work as a multigrade and are therefore less prone to viscosty loss by shearing.

Cheers
Simon Read more

Had a lift in a new CRV Automatic yesterday.A very smooth and comfortable vehicle.
Gear shift lever on dashboard was a novel sight.
Do these vehicles have any over ride buttons/levers for when the going gets tricky e.g. snow? The owner tells me he bought it for his wife to commute to Buxton, Derbyshire.
--
I wasna fu but just had plenty. Read more

Hi,
I own a V Reg Peugeot 306 Automatic (from new) and recently have started to have a problem with the engine stalling when at traffic lights / junctions - this could happen in any weather conditions and makes no difference if the car is cold/hot. It doesn't always stall sometimes it is fine and other times the revs will just drop and the engine will cut out.
I've scoured the net trying to find an answer to the problem as my local peugeot garage can't find anything wrong! it's been hooked up to their computer many times and nothing has been reported.
On reading others experiencing the same problem in forums on the net it seemed there was two faults that was the likely culprit - The Stepper Motor Idle Controller or a damaged ECU.
Armed with this information I went back to my dealer and asked them to change the Stepper Motor Idle Controller hoping this would fix the problem....but, no. A new stepper motor was installed and the problem persisted. My peugeot garage then suggested sending the ECU to a company who could repair them - which I did, but I've just heard back from them saying the ECU has no problems and is working fine!

So, has anyone else had this kind of problem? Is there anyone with any idea of the next step I can take? The peugeot garage seems to be out of ideas now and my car has been stuck in their garage for the last 6 weeks, but I'm still no closer to having it repaired :(

Thanks in advance to anyone who may be able to help! Read more

Picture the scene. It's dark, raining hounds and kittens and it's rush hour. Traffic is moving forward in fits and starts, maybe 50 yards at 5-10 mph, then 200 yards at 20 or so. It's a typical suburban A-road with traffic islands, side roads and chevroned right-turn refuges. The road is straight as a die for 4 miles.

I'm making my way along this road on my pushbike at around 18-20mph. I have a full high-viz coat on, and have a matching cover for my rucksack. I have a solid red light on the bike, a scrolling red led light on the back of my helmet and a flashing red armband all showing to the rear. To the front I have a twin 15-25w Cateye Halogen headlamp set on the bike and a flashing white led at shoulder level on the rucksack straps. In short, I'm HIGHLY visible.

In the free-flowing bits I was riding mid-lane as my speed matched the flow of traffic. In slower bits I overtook to the outside as you would on a motorbike. When riding with the traffic flow I kept a couple of car lengths back from the car in front to allow for braking or other avoiding action.

So WHY ON EARTH did I find that in those 4 miles, 5 cars overtook me into this miniscule space only to immediately cut back across me and brake hard to avoid running into the car in front of us? Within seconds the traffic had slowed (and was clearly visible as having slowed ahead) and I was overtaking these people again. In each case I had to take avoiding action, including hopping on to the kerb in one instance to avoid becoming another RTA statistic.

What is the obsession with being in front of a cyclist? A cyclist who is clearly maintaining or exceeding the speed of the traffic, who is highly visible and is overtaking correctly when opportunities present?

If anyone can see what I'm doing wrong I'll gladly learn from it. I have no desire to pass the proceeds of our joint life policies to my beloved wife just to prove a point. Read more