Hello,
I would like to know if Avast uses many engines or if it relies on one only because I have noticed that this has been an issue and that some people have said that the engine was part of the problem and since no engine is capable of been able to detect all the viruses using at least two engine would enable the possibility of detecting all the virus and malware. I know that Kaspersky has done so if they can do it so can Avast. Rights ??
MounierNetwork
avast! uses only its own engine.
Multi-engine AV, however, is not such a miracle as you might think. First, there’s no guarantee that 2 engines detect all the viruses (they don’t, of course - you might have a new piece of malware that none of the engines on Jotti / VirusTotal detect, but it’s still malware). Actually, there’s no guarantee that there’s any improvement if you add the second engine (what if the detection of the second engine is a subset of the first one?)
In reality, the improvement in going from one engine to two will be rather small, IMHO.
Appart from the licensing stuff (you will have to pay more for 2 engines than for one, because the other vendor wants some money, too), there are other disadvantages as well - the false positives sum up from the two engines, the scanning is slower (because you actually scan everything twice)…
Ok
How about once more kaspersky ,I believe they have very few false possitive and their scanning time is good and not too pricy ??
MounierNetwork
It’s a pity that such a good scanner and antivirus couldn’t be used as a non-resident… for free :-\ 
I didn’t specificly meant 2 engines I just meant more than one 
It is almost sure that more virus will be able to be detected. 
Don’t you think so ?
Mounier Network
The performance will drop down dramatically I can imagine…
Is the same of having two residents that uses a lot of system resources at the same time : ???
If you want a multi-engine AV product you can try e.g. AVK
http://www.gdatasoftware.com/